Variable stiffness support system and variable stiffness tension system

Abstract

This invention relates to the field of 3D material printing technology, and more particularly to a variable stiffness support system and a variable stiffness tension system. Both the variable stiffness support system and the variable stiffness tension system include multiple substrates and multiple elastic elements, one of which possesses a maximum force, thereby enabling series and parallel connection conversion of the multiple elastic elements under different conditions. The variable stiffness support system and variable stiffness tension system provided by this invention, through the aforementioned series and parallel connection conversion of the elastic elements, allow the overall structure of the support system and tension system to exhibit stiffness hardening characteristics. Moreover, during series and parallel connection conversion, the overall structural deformation suddenly decreases with increasing force, exhibiting rare negative compressive or negative tensile properties, and has broad application prospects.

Description

Technical Field

[0001] This invention relates to the field of 3D material printing technology, and in particular to a variable stiffness support system and a variable stiffness tension system. Background Technology

[0002] When an elastic body is subjected to tension or compression, it generates a force that resists deformation. To describe the degree to which an object responds to external forces and resists deformation, the physical quantity stiffness is defined as the derivative of the resistance with respect to the amount of deformation. It is important to note that stiffness and the elastic modulus are similar in meaning but not the same. The elastic modulus is a fundamental property of the material itself, while stiffness is a property of the entire structure, influenced not only by the material properties of the constituent materials but also by the structural shape and boundary conditions. For most structures, stiffness is constant when the deformation is not too large, exhibiting linear elasticity. However, by rationally designing the structural shape, stiffness can be made to change with the amount of deformation, exhibiting variable stiffness characteristics. Common variable stiffness characteristics include: stiffness hardening, where the larger the deformation, the greater the increase in load required to produce a unit deformation, resulting in a structure becoming increasingly "stiff"; and stiffness softening, where the larger the deformation, the smaller the increase in load required to produce a unit deformation, resulting in a structure becoming increasingly "soft." Variable stiffness properties have broad application prospects and can be used for wave manipulation, resonance suppression, and load adaptation. In particular, the bistable nature of the structure means that the force it provides has a definite upper limit, thus enabling it to flexibly absorb large impacts and exhibiting excellent buffering and energy absorption properties. In fact, these specially designed structures can be classified as "metamaterials." While there is no universally agreed-upon definition of metamaterials, the academic community generally agrees that they possess two key characteristics: they exhibit unconventional properties different from traditional materials; and these properties originate from the metamaterial's spatial structure, rather than the materials that constitute it.

[0003] Existing variable stiffness metamaterial structures have certain shortcomings. The unconventional characteristics of most structures are manifested in negative stiffness and the resulting bistable or self-restoring properties. Many studies have also focused on stiffness hardening or softening. However, in these structures, force is always a single-valued function of deformation, meaning that the deformation corresponding to a force is unique, and it is impossible for a force to correspond to multiple deformations. Furthermore, most materials always contract (or elongate) along the direction of compression (or tension) when subjected to compression (or tension), and cannot elongate (or shorten) against the direction of compression (or tension), i.e., negative compressibility (or negative tensile property). This property is extremely rare in academia and industry and has great potential for applications in force sensors, actuators, and other fields. Summary of the Invention

[0004] This invention provides a variable stiffness support system and a variable stiffness tension system to solve the defects in existing variable stiffness material structures where the force is always a single-valued function of the deformation and does not have negative compressibility or negative tensile properties.

[0005] This invention provides a variable stiffness support system, comprising:

[0006] First substrate;

[0007] The second substrate is disposed opposite to the first substrate;

[0008] A third substrate, wherein the third substrate is located between the first substrate and the second substrate;

[0009] A first elastic element, one end of which is connected to the first substrate, and the other end of which is connected to one end of the third substrate;

[0010] A fourth substrate, wherein the fourth substrate is located between the first substrate and the second substrate, and one end of the fourth substrate is located between the first substrate and the third substrate;

[0011] The second elastic element has one end connected to the other end of the third substrate and the other end connected to one end of the fourth substrate.

[0012] A third elastic element, one end of which is connected to the other end of the fourth substrate, and the other end of which is connected to the second substrate;

[0013] Under the first condition, there is a gap between the first substrate, the fourth substrate, the third substrate and the second substrate;

[0014] Under the second condition, the third substrate is bonded to the second substrate, and the fourth substrate is bonded to the first substrate.

[0015] According to the present invention, a variable stiffness support system is provided, wherein the second elastic element has a maximum force value; the first condition is that the pressure between the first substrate and the second substrate is less than the maximum force value of the second elastic element; and the second condition is that the pressure between the first substrate and the second substrate is greater than the maximum force value of the second elastic element.

[0016] According to a variable stiffness support system provided by the present invention, the second elastic element includes: a polylactic acid elastic element, a thermoplastic polyurethane elastic element, or a polyurethane elastic element; under the first condition, by changing the temperature of the environment in which the second elastic element is located, the maximum value of the force of the second elastic element is reduced, thereby transforming into the second condition; or, under the second condition, by changing the temperature of the environment in which the second elastic element is located, the critical value of the force of the second elastic element is increased, thereby transforming into the first condition.

[0017] According to the present invention, a variable stiffness support system is provided, wherein the first elastic element and the third elastic element are both elastic elements made of positive stiffness material.

[0018] According to the present invention, a variable stiffness support system is provided, wherein the first elastic element and the third elastic element are both compression springs.

[0019] This invention also provides a tension system with variable stiffness, comprising:

[0020] Fifth substrate;

[0021] The sixth substrate is disposed opposite to the fifth substrate;

[0022] A seventh substrate is located between the fifth substrate and the sixth substrate;

[0023] The fourth elastic element has one end connected to the fifth substrate and the other end connected to one end of the seventh substrate.

[0024] An eighth substrate, wherein the eighth substrate is located between the fifth substrate and the sixth substrate, and one end of the eighth substrate is located between the sixth substrate and the seventh substrate;

[0025] The fifth elastic element has one end connected to the other end of the seventh substrate and the other end connected to one end of the eighth substrate.

[0026] A sixth elastic element, one end of which is connected to the other end of the eighth substrate, and the other end of which is connected to the sixth substrate;

[0027] The first limiting member is fixedly connected to the fifth substrate and is used to limit the eighth substrate.

[0028] The second limiting member is fixedly connected to the sixth substrate and is used to limit the seventh substrate.

[0029] Under the third condition, there is a gap between the first limiting member and the eighth substrate, and a gap between the second limiting member and the seventh substrate.

[0030] Under the fourth condition, the first limiting member is bonded and limited to the eighth substrate, and the second limiting member is bonded and limited to the seventh substrate.

[0031] According to the present invention, a variable stiffness tension system is provided in which the fifth elastic element has a maximum force; the third condition is that the tensile force between the fifth substrate and the sixth substrate is less than the maximum force of the fifth elastic element; and the fourth condition is that the tensile force between the fifth substrate and the sixth substrate is greater than the maximum force of the fifth elastic element.

[0032] According to the present invention, a variable stiffness tension system is provided, wherein the fifth elastic element comprises: a polylactic acid elastic element, a thermoplastic polyurethane elastic element, or a polyurethane elastic element; under the third condition, by changing the temperature of the environment in which the fifth elastic element is located, the maximum value of the force of the fifth elastic element is reduced, thereby transforming into the fourth condition; or, under the fourth condition, by changing the temperature of the environment in which the fifth elastic element is located, the critical value of the force of the fifth elastic element is increased, thereby transforming into the third condition.

[0033] According to the present invention, in a variable stiffness tension system, the fourth elastic element and the sixth elastic element are both elastic elements made of positive stiffness material.

[0034] According to the present invention, in a variable stiffness tension system, both the first limiting member and the second limiting member are rigid material limiting members.

[0035] The present invention provides a variable stiffness support system, comprising: a first substrate, a second substrate, a third substrate, a first elastic element, a fourth substrate, a second elastic element, and a third elastic element; the first substrate, the fourth substrate, the third substrate, and the second substrate are stacked sequentially, the first elastic element is connected between the first substrate and the third substrate, the second elastic element is connected between the third substrate and the fourth substrate, and the third elastic element is connected between the fourth substrate and the second substrate; under a first condition, there is a gap between the first substrate, the fourth substrate, the third substrate, and the second substrate; under a second condition, the third substrate and the second substrate are bonded together, and the fourth substrate and the first substrate are bonded together. The present invention provides a variable stiffness support system. Under a first condition, the first, second, and third elastic elements are connected in series in their tension and compression directions, resulting in a relatively low overall stiffness of the support system. Under a second condition, the first, second, and third elastic elements are connected in parallel, resulting in a relatively high overall stiffness of the support system. Through the aforementioned series-parallel conversion of the elastic elements, the overall structure of the support system can exhibit stiffness hardening characteristics. Moreover, during the series-parallel conversion, the overall deformation of the structure suddenly decreases with the increase of force, exhibiting rare negative compressibility, and has broad application prospects.

[0036] This invention provides a variable stiffness tension system, comprising: a fifth substrate, a sixth substrate, a seventh substrate, a fourth elastic element, an eighth substrate, a fifth elastic element, a sixth elastic element, a first limiting element, and a second limiting element; the fifth substrate, the seventh substrate, the eighth substrate, and the sixth substrate are stacked sequentially, the fourth elastic element is connected between the fifth substrate and the seventh substrate, the fifth elastic element is connected between the seventh substrate and the eighth substrate, the sixth elastic element is connected between the eighth substrate and the sixth substrate, and the first limiting element and the second limiting element are respectively used to limit the eighth substrate and the seventh substrate; under a third condition, there is a gap between the first limiting element and the eighth substrate, and a gap between the second limiting element and the seventh substrate; under a fourth condition, the first limiting element is fitted and limited to the eighth substrate, and the second limiting element is fitted and limited to the seventh substrate. The present invention provides a variable stiffness tension system. Under the third condition, the overall stiffness of the tension system is relatively small because the fourth, fifth, and sixth elastic elements are connected in series in the tension and compression directions. Under the fourth condition, the overall stiffness of the tension system is relatively large because the fourth, fifth, and sixth elastic elements are connected in parallel. Through the above-mentioned series and parallel connection conversion of elastic elements, the overall structure of the tension system can exhibit stiffness hardening characteristics. Moreover, during the series and parallel connection conversion, the overall deformation of the structure suddenly decreases with the increase of force, exhibiting rare negative tensile properties, and has broad application prospects. Attached Figure Description

[0037] To more clearly illustrate the technical solutions in this invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0038] Figure 1 This is a schematic diagram of the structure of the variable stiffness support system provided in Embodiment 1 of the present invention when the elastic elements are connected in series;

[0039] Figure 2 This is a schematic diagram of the structure of the variable stiffness support system provided in Embodiment 1 of the present invention when the elastic elements are connected in parallel;

[0040] Figure 3 This is a schematic diagram of the structure of the variable stiffness tension system provided in Embodiment 2 of the present invention when the elastic elements are connected in series;

[0041] Figure 4 This is a schematic diagram of the structure of the variable stiffness tension system provided in Embodiment 2 of the present invention when the elastic elements are connected in parallel.

[0042] Figure label:

[0043] 1: First substrate; 2: Second substrate; 3: Third substrate; 4: Fourth substrate; 5: First elastic element; 6: Second elastic element; 7: Third elastic element;

[0044] 8: Fifth substrate; 9: Sixth substrate; 10: Seventh substrate; 11: Eighth substrate; 12: Fourth elastic member; 13: Fifth elastic member; 14: Sixth elastic member; 15: First limiting member; 16: Second limiting member. Detailed Implementation

[0045] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this invention. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0046] In the description of the embodiments of the present invention, it should be noted that the terms "center," "longitudinal," "lateral," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing the embodiments of the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the embodiments of the present invention. In addition, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0047] In the description of the embodiments of the present invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "connected" and "linked" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium. Those skilled in the art can understand the specific meaning of the above terms in the embodiments of the present invention based on the specific circumstances.

[0048] In embodiments of the present invention, unless otherwise explicitly specified and limited, "above" or "below" the second feature can mean that the first feature is in direct contact with the second feature, or that the first feature is in indirect contact with the second feature through an intermediate medium. Furthermore, "above," "on top of," and "over" the second feature can mean that the first feature is directly above or diagonally above the second feature, or simply that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature can mean that the first feature is directly below or diagonally below the second feature, or simply that the first feature is at a lower horizontal level than the second feature.

[0049] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., refer to specific features, structures, materials, or characteristics described in connection with that embodiment or example, which are included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0050] The following is combined Figure 1 and Figure 2 This invention describes a variable stiffness support system according to Embodiment 1. The support system includes: a first substrate 1, a second substrate 2, a third substrate 3, a first elastic member 5, a fourth substrate 4, a second elastic member 6, and a third elastic member 7.

[0051] The second substrate 2 is disposed opposite to the first substrate 1; the third substrate 3 is located between the first substrate 1 and the second substrate 2; one end of the first elastic member 5 is connected to the first substrate 1, and the other end of the first elastic member 5 is connected to one end of the third substrate 3; the fourth substrate 4 is located between the first substrate 1 and the second substrate 2, and one end of the fourth substrate 4 is located between the first substrate 1 and the third substrate 3; one end of the second elastic member 6 is connected to the other end of the third substrate 3, and the other end of the second elastic member 6 is connected to one end of the fourth substrate 4; one end of the third elastic member 7 is connected to the other end of the fourth substrate 4, and the other end of the third elastic member 7 is connected to the second substrate 2.

[0052] Specifically, under the first condition, there is a gap between the first substrate 1, the fourth substrate 4, the third substrate 3, and the second substrate 2; under the second condition, the third substrate 3 is bonded to the second substrate 2, and the fourth substrate 4 is bonded to the first substrate 1. It should be understood that the first and second conditions can be caused by different temperature conditions, pressure conditions, light conditions, etc., resulting in changes in the connection relationship between the elastic elements: under the first condition, the first elastic element 5, the second elastic element 6, and the third elastic element 7 are connected in series in their tension / compression direction; under the second condition, the first elastic element 5, the second elastic element 6, and the third elastic element 7 are connected in parallel. To achieve the switching between the first and second conditions, the external force applied to the support system can be changed, or the environmental conditions can be changed to alter the mechanical properties of the second elastic element 6, thereby achieving the mutual conversion between the first and second conditions. Alternatively, these two methods can be combined to achieve the desired effect.

[0053] Specifically, the variable stiffness support system of Embodiment 1 of the present invention is applied to change the tension and compression states of the first elastic element 5, the second elastic element 6 and the third elastic element 7 according to the conditions. However, no matter how the conditions change, the first substrate 1 and the second substrate 2 are always arranged opposite each other, the third substrate 3 is always located between the first substrate 1 and the second substrate 2, one end of the fourth substrate 4 is located between the third substrate 3 and the first substrate 1, and the other end of the fourth substrate 4 is located between the first substrate 1 and the second substrate 2.

[0054] The second elastic element 6 has a maximum force. Based on its mechanical properties, under the first condition, since the first substrate 1, fourth substrate 4, third substrate 3, and second substrate 2 are all spaced apart, the first elastic element 5, second elastic element 6, and third elastic element 7 are connected in series in their tension and compression directions. This series connection can be understood as equivalently forming an elastic element with a small elastic modulus, i.e., as... Figure 1 The structure shown; under the first condition, the first elastic element 5 and the third elastic element 7 are both in a compressed state, and the second elastic element 6 is in a stretched state. Because the second elastic element 6 has a maximum force, it remains in a continuously stretched state until the external force reaches its maximum value. As the external force increases, the second elastic element 6 cannot withstand such a large force, and the stretch increases rapidly until the third substrate 3 is bonded to the second substrate 2 and the fourth substrate 4 is bonded to the first substrate 1, thus reaching the second condition. At this point, the first elastic element 5, the second elastic element 6, and the third elastic element 7 are connected in parallel. This parallel connection can be understood as treating the first elastic element 5, the second elastic element 6, and the third elastic element 7 as an equivalent elastic element with a large elastic modulus, i.e., as... Figure 2The structure shown here refers to an "elastic element with a larger elastic modulus" in comparison to the "elastic element with a smaller elastic modulus" mentioned above. In summary, under the first condition, because the first elastic element 5, the second elastic element 6, and the third elastic element 7 are connected in series in their tensile and compressive directions, the overall stiffness of the support system is relatively small; under the second condition, because the first elastic element 5, the second elastic element 6, and the third elastic element 7 are connected in parallel, the overall stiffness of the support system is relatively large.

[0055] The above process has demonstrated the stiffness hardening characteristics of the structure. It is worth noting that the stiffness hardening characteristics here appear "passively" during the increase of external force. Stiffness hardening can also be "actively" induced by other external means to change the structure from a series connection of elastic elements to a parallel connection. The methods can be: artificially damaging the second elastic element 6 to make it fail and unable to withstand tensile force; reducing the maximum value of the second elastic element 6 by means of softening through heating, etc.

[0056] The second elastic element 6 is a type of component possessing a maximum force value. It can be a component with a negative stiffness segment, a component capable of releasing contact, or other types of components, as long as the relationship between its maximum force value and the applied external force can be adjusted under specific conditions. The first elastic element 5 and the third elastic element 7 can be various types of elastic elements. During the triggering process of series-parallel conversion, the negative stiffness segment of the second elastic element 6 can be passively triggered by external pressure or tension to achieve series-parallel conversion, or the series-parallel conversion can be actively triggered by means of temperature, light, etc.

[0057] This variable stiffness support system also has a more special anomalous characteristic: during series-parallel conversion, the overall deformation of the structure will decrease sharply as the force increases.

[0058] For the sake of simplicity, the force-displacement relationship of the first elastic element 5, the second elastic element 6, and the third elastic element 7 will be assumed as follows for the continued discussion:

[0059] F5 = k5x5

[0060] F7 = k7x7

[0061]

[0062] In the above formula, F5, F6, and F7 are the elastic forces of the first elastic element 5, the second elastic element 6, and the third elastic element 7, respectively; k5 and k7 are the elastic moduli of the first elastic element 5 and the third elastic element 7, respectively; and x5, x6, and x7 are the deformations of the first elastic element 5, the second elastic element 6, and the third elastic element 7, respectively. c Let k6 be the maximum force of the second elastic element 6, and k6 be the force of the second elastic element 6 when the deformation is less than x.c The elastic modulus at time x, k′6 is the second elastic element 6 when the deformation is greater than x. c And less than x m The incremental elastic modulus at time t, any refers to the value when the deformation of the second elastic element 6 is greater than x. m After that, it no longer has negative stiffness characteristics, which is meaningless for subsequent theoretical derivations, so its specific form is no longer of concern.

[0063] Note that here we assume the first elastic element 5 and the third elastic element 7 are the same elastic element with constant and equal stiffness; the stiffness of the second elastic element 6 is constant in segments, with one segment of negative stiffness, and x6 > x m The stiffness becomes positive, but its specific form is no longer a concern. In fact, the stiffness of the first elastic element 5 and the third elastic element 7 may not be constant, and the stiffness and original length may not be equal. The second elastic element 6 may not necessarily conform to the above form either; it only needs to have a maximum value within a certain range of deformation.

[0064] The distance between the first substrate 1 and the second substrate 2 is defined as H. When connected in series, the distance between the first substrate 1 and the second substrate 2 is H. s When connected in parallel, the distance between the first substrate 1 and the second substrate 2 is H. p Consider the force F on the substrate. c The critical state. When the first elastic element 5, the second elastic element 6, and the third elastic element 7 are connected in series, the following relationship is satisfied.

[0065]

[0066] Where, Δx 57 Numerically equal to the deformation of the first elastic element 5 or the third elastic element 7 when connected in series, since the deformation of the first elastic element 5 and the third elastic element 7 are equal, therefore, Δx 57 Numerically equal to Δx5 or Δx7, all three are equal, and l in the following formula 57 and Δx 57 Similarly, Δx6 is the deformation of the second elastic element 6 when connected in series, where k 57 Let k5 and k7 be the elastic moduli of the first elastic element 5 or the third elastic element 7 when connected in series. They are equal and equal to k5 and k7 in the above formula. Therefore, when connected in series, we have:

[0067]

[0068] Among them, l 57 Numerically equal to the original length of the first elastic element 5 or the third elastic element 7, all three are equal, and l6 is the original length of the second elastic element 6. When the first elastic element 5, the second elastic element 6, and the third elastic element 7 just become parallel, the force on the first substrate 1 can be considered to still be F. c The following relation is satisfied:

[0069]

[0070] Where, Δx 57 The value of Δx6′ is numerically equal to the deformation of the first elastic element 5 or the third elastic element 7 in parallel connection, and all three are equal. Δx6′ is the deformation of the second elastic element 6 in parallel connection, and F′6 is the elastic force generated by the second elastic element 6 when it deforms by Δx6′. Therefore, in parallel connection, we have:

[0071]

[0072] Compare H s With H p get

[0073]

[0074] Furthermore, geometric relationships can be obtained...

[0075]

[0076] Note that when At that time, it can be obtained

[0077] Δ≥0

[0078] That is, when the pressure on the first substrate 1 is from F c With a slight increase, after the connection structure of the elastic components in the entire support system changed from a series state to a parallel state, the first substrate 1 did not drop but rose instead, and the overall deformation of the structure suddenly decreased. The structure has extremely negative compressibility near the critical value, which shows rare anomalous characteristics.

[0079] In addition to increasing pressure and thus causing a shift from series to parallel connections, it is also possible to change F. c The size is implemented. For example, F c Proportional to the elastic modulus of the second elastic element 6, therefore, while keeping the external force constant, factors such as temperature and light exposure of the second elastic element can be changed to reduce the Young's modulus of the elastic element, thus reducing F. c When the force is reduced to less than the external force, the support system changes from a series connection to a parallel connection.

[0080] The above illustrates the transition from separation to contact between the substrates in this invention, which is a loading process, i.e., a gradual increase in external force from 0. Interestingly, during the unloading process, i.e., as the external force gradually decreases to 0, the force response curves differ, forming a hysteresis loop. During the unloading process, when the substrates are about to separate from each other, the following set of equations is satisfied:

[0081]

[0082] Therefore, the external force is less than

[0083]

[0084] At this time, the substrates separate from each other, changing from a parallel state to a series state, where F e This is the critical value during the unloading process. By changing the temperature of the environment where the second elastic element 6 is located, the critical value of the force of the second elastic element 6 is increased, thus transforming it into the first condition. Therefore, to make the substrate change from a contact state to a separation state, that is, from a parallel state to a series state, the external force can be reduced until it is less than F. e Furthermore, it is noted that k6 and k′6 are both proportional to the elastic modulus of the second elastic element 6. Therefore, by changing the elastic modulus through means such as temperature and light, F can be changed. e When F e When the force exceeds the external force, the substrates may also separate.

[0085] The present invention provides a variable stiffness support system, comprising: a first substrate 1, a second substrate 2, a third substrate 3, a first elastic element 5, a fourth substrate 4, a second elastic element 6, and a third elastic element 7; the first substrate 1, the fourth substrate 4, the third substrate 3, and the second substrate 2 are stacked sequentially, the first elastic element 5 is connected between the first substrate 1 and the third substrate 3, the second elastic element 6 is connected between the third substrate 3 and the fourth substrate 4, and the third elastic element 7 is connected between the fourth substrate 4 and the second substrate 2; under a first condition, there is a gap between the first substrate 1, the fourth substrate 4, the third substrate 3, and the second substrate 2; under a second condition, the third substrate 3 is bonded to the second substrate 2, and the fourth substrate 4 is bonded to the first substrate 1. The present invention provides a variable stiffness support system. Under the first condition, since the first elastic element 5, the second elastic element 6, and the third elastic element 7 are connected in series in their tension and compression directions, the overall stiffness of the support system is relatively small. Under the second condition, since the first elastic element 5, the second elastic element 6, and the third elastic element 7 are connected in parallel, the overall stiffness of the support system is relatively large. Through the above-mentioned series and parallel connection conversion of elastic elements, the overall structure of the support system can exhibit stiffness hardening characteristics. Moreover, during the series and parallel connection conversion, the overall deformation of the structure will suddenly decrease with the increase of force, exhibiting rare negative compressibility, and has broad application prospects.

[0086] In one embodiment of the present invention, the second elastic member 6 has a maximum force value; the first condition is that the pressure between the first substrate 1 and the second substrate 2 is less than the maximum force value of the second elastic member 6; the second condition is that the pressure between the first substrate 1 and the second substrate 2 is greater than the maximum force value of the second elastic member 6. In this embodiment, the first and second conditions are switched by changing the relationship between the pressure between the first substrate 1 and the second substrate 2 and the maximum force value of the second elastic member 6.

[0087] In one embodiment of the present invention, the second elastic member 6 includes: a polylactic acid elastic member, a thermoplastic polyurethane elastic member, or a polyurethane elastic member; under the first condition, by changing the temperature of the environment in which the second elastic member 6 is located, the maximum value of the force of the second elastic member 6 is reduced, thereby transforming into the second condition; or, under the second condition, by changing the temperature of the environment in which the second elastic member 6 is located, the critical value of the force of the second elastic member 6 (i.e., F in the above formula) is increased. e This transforms the first condition into the second condition. Besides applying different external forces to achieve the transition between the first and second conditions, in this embodiment, the special properties of special materials can also be utilized to achieve the above effect. For example, materials such as polylactic acid and thermoplastic polyurethane exhibit different Young's moduli at different temperatures. Increasing the temperature can lower their Young's modulus, thereby changing the maximum value of their force. This allows adjustment of the relationship between the applied external force and the maximum (or critical) value of the force of the second elastic element 6 without changing the applied external force, thus achieving the transition between the first and second conditions.

[0088] In one embodiment of the present invention, the first elastic element 5 and the third elastic element 7 are both elastic elements made of positive stiffness material; preferably, the first elastic element 5 and the third elastic element 7 are both compression springs.

[0089] It should be understood that the variable stiffness support system in the above embodiments can be a two-dimensional structure or a three-dimensional structure.

[0090] The following is combined Figure 3 and Figure 4 This invention describes a variable stiffness tension system according to Embodiment 2. The variable stiffness tension system includes: a fifth substrate 8, a sixth substrate 9, a seventh substrate 10, a fourth elastic member 12, an eighth substrate 11, a fifth elastic member 13, a sixth elastic member 14, a first limiting member 15, and a second limiting member 16. The variable stiffness support system of Embodiment 1 is primarily used in compressive environments, while the variable stiffness tension system of Embodiment 2 is primarily used in tensile environments.

[0091] The fifth substrate 8 and the sixth substrate 9 are disposed opposite to each other; the seventh substrate 10 is located between the fifth substrate 8 and the sixth substrate 9; one end of the fourth elastic member 12 is connected to the fifth substrate 8, and the other end of the fourth elastic member 12 is connected to one end of the seventh substrate 10; the eighth substrate 11 is located between the fifth substrate 8 and the sixth substrate 9, and one end of the eighth substrate 11 is located between the sixth substrate 9 and the seventh substrate 10; one end of the fifth elastic member 13 is connected to the other end of the seventh substrate 10, and the other end of the fifth elastic member 13 is connected to one end of the eighth substrate 11; one end of the sixth elastic member 14 is connected to the other end of the eighth substrate 11, and the other end of the sixth elastic member 14 is connected to the sixth substrate 9; the first limiting member 15 is fixedly connected to the fifth substrate 8 and is used to limit the eighth substrate 11; the second limiting member 16 is fixedly connected to the sixth substrate 9 and is used to limit the seventh substrate 10.

[0092] Specifically, under the third condition, there is a gap between the first limiting member 15 and the eighth substrate 11, and a gap between the second limiting member 16 and the seventh substrate 10; under the fourth condition, the first limiting member 15 is fitted and limited to the eighth substrate 11, and the second limiting member 16 is fitted and limited to the seventh substrate 10. It should be understood that the third and fourth conditions can be different temperature conditions, pressure conditions, light conditions, etc., which change the connection relationship between the elastic members: under the third condition, since there is a gap between the first limiting member 15 and the eighth substrate 11 (that is, they are not fitted and limited), and there is a gap between the second limiting member 16 and the seventh substrate 10 (that is, they are not fitted and limited), the fourth elastic member 12, the fifth elastic member 13, and the sixth elastic member 14 are connected in series in their tension and compression directions; under the fourth condition, the fourth elastic member 12, the fifth elastic member 13, and the sixth elastic member 14 are connected in parallel. To achieve the switching between the third and fourth conditions mentioned above, the external force applied to the tension system can be changed, or the environmental conditions can be changed to alter the mechanical properties of the fifth elastic element 13, thereby achieving the mutual conversion between the third and fourth conditions. Of course, the two methods mentioned above can also be combined to achieve the desired effect.

[0093] Specifically, the variable stiffness tension system of Embodiment 2 of the present invention is applied to change the tension and compression states of the fourth elastic element 12, the fifth elastic element 13 and the sixth elastic element 14 according to the conditions. However, no matter how the conditions change, the fifth substrate 8 and the sixth substrate 9 are always arranged opposite each other, the seventh substrate 10 is always located between the fifth substrate 8 and the sixth substrate 9, one end of the eighth substrate 11 is located between the seventh substrate 10 and the sixth substrate 9, and the other end of the eighth substrate 11 is located between the fifth substrate 8 and the sixth substrate 9.

[0094] The fifth elastic element 13 has a maximum force. Based on its mechanical properties, under the third condition, since the first limiting element 15 and the eighth substrate 11 are not in contact, and the second limiting element 16 and the seventh substrate 10 are not in contact, the fourth elastic element 12, the fifth elastic element 13, and the sixth elastic element 14 are connected in series in their tension and compression directions. This series connection can be understood as equivalently forming an elastic element with a small elastic modulus, i.e., as... Figure 3 The structure shown; under the third condition, the applied tensile force continuously increases. When the applied force exceeds the maximum value of the force of the fifth elastic element 13, the fifth elastic element 13 will rapidly elongate because it cannot withstand the enormous tensile force, until the first limiting element 15 is fitted and limited to the eighth substrate 11, and the second limiting element 16 is fitted and limited to the seventh substrate 10, thus reaching the fourth condition. At this time, the fourth elastic element 12, the fifth elastic element 13, and the sixth elastic element 14 are connected in parallel. The above parallel connection can be understood as equivalent to the fourth elastic element 12, the fifth elastic element 13, and the sixth elastic element 14 being a single elastic element with a large elastic modulus, i.e., as shown. Figure 4 The structure shown here refers to an "elastic element with a larger elastic modulus" compared to the "elastic element with a smaller elastic modulus" mentioned above. In summary, under the third condition, because the fourth elastic element 12, the fifth elastic element 13, and the sixth elastic element 14 are connected in series in their tension and compression directions, the overall stiffness of the tension system is relatively small; under the fourth condition, because the fourth elastic element 12, the fifth elastic element 13, and the sixth elastic element 14 are connected in parallel, the overall stiffness of the tension system is relatively large.

[0095] The above process has demonstrated the stiffness hardening characteristics of the structure. It is worth noting that the stiffness hardening characteristics here appear "passively" during the increase of external force. Stiffness hardening of the structure can also be "actively" induced by other external means to change the structure from a series connection of elastic elements to a parallel connection. The methods can be: artificially damaging the fifth elastic element 13 to make it fail and unable to withstand tensile force; reducing the maximum value of the fifth elastic element 13 by means of softening through heating, etc.

[0096] The fifth elastic element 13 is a type of component possessing a maximum force value. It can be a component with a negative stiffness segment, a component capable of releasing contact, or other types of components, as long as the relationship between its maximum force value and the applied external force can be adjusted under specific conditions. The fourth elastic element 12 and the sixth elastic element 14 can be various types of elastic elements. During the triggering process of series-parallel conversion, the fifth elastic element 13 can be passively triggered by external pressure or tension to achieve series-parallel conversion, or it can be actively triggered by means of temperature, light, etc.

[0097] This variable stiffness tension system also has a more special anomalous characteristic: when the series-parallel connection is converted, the overall deformation of the structure will decrease sharply as the force increases. The reasoning process is the same as the principle in Example 1, and will not be repeated here.

[0098] The present invention provides a variable stiffness tension system comprising: a fifth substrate 8, a sixth substrate 9, a seventh substrate 10, a fourth elastic member 12, an eighth substrate 11, a fifth elastic member 13, a sixth elastic member 14, a first limiting member 15, and a second limiting member 16; the fifth substrate 8, the seventh substrate 10, the eighth substrate 11, and the sixth substrate 9 are stacked sequentially; the fourth elastic member 12 is connected between the fifth substrate 8 and the seventh substrate 10; the fifth elastic member 13 is connected between the seventh substrate 10 and the eighth substrate 11; the sixth elastic member 14 is connected between the eighth substrate 11 and the sixth substrate 9; the first limiting member 15 and the second limiting member 16 are respectively used to limit the eighth substrate 11 and the seventh substrate 10; under a third condition, there is a gap between the first limiting member 15 and the eighth substrate 11, and a gap between the second limiting member 16 and the seventh substrate 10; under a fourth condition, the first limiting member 15 is fitted and limited to the eighth substrate 11, and the second limiting member 16 is fitted and limited to the seventh substrate 10. The present invention provides a variable stiffness tension system. Under the third condition, the overall stiffness of the tension system is relatively small because the fourth elastic element 12, the fifth elastic element 13, and the sixth elastic element 14 are connected in series in the tension and compression directions. Under the fourth condition, the overall stiffness of the tension system is relatively large because the fourth elastic element 12, the fifth elastic element 13, and the sixth elastic element 14 are connected in parallel. Through the above-mentioned series and parallel connection conversion of elastic elements, the overall structure of the tension system can exhibit stiffness hardening characteristics. Moreover, during the series and parallel connection conversion, the overall deformation of the structure suddenly decreases with the increase of force, exhibiting rare negative tensile properties, and has broad application prospects.

[0099] In one embodiment of the present invention, the fifth elastic member 13 has a maximum force; the third condition is that the tensile force between the fifth substrate 8 and the sixth substrate 9 is less than the maximum force of the fifth elastic member 13; the fourth condition is that the tensile force between the fifth substrate 8 and the sixth substrate 9 is greater than the maximum force of the fifth elastic member 13. In this embodiment, the switching between the third and fourth conditions is achieved by changing the relationship between the tensile force between the fifth substrate 8 and the sixth substrate 9 and the maximum force of the fifth elastic member 13.

[0100] In one embodiment of the present invention, the fifth elastic element 13 includes: a polylactic acid elastic element, a thermoplastic polyurethane elastic element, or a polyurethane elastic element; under the third condition, by changing the temperature of the environment in which the fifth elastic element 13 is located, the maximum value of the force of the fifth elastic element 13 is reduced, thereby transforming into the fourth condition; or, under the fourth condition, by changing the temperature of the environment in which the fifth elastic element 13 is located, the critical value of the force of the fifth elastic element 13 is increased, thereby transforming into the third condition. In this embodiment, in addition to applying different external forces to achieve the conversion between the third and fourth conditions, the above-mentioned effects can also be achieved by utilizing the special properties of special materials. For example, materials such as polylactic acid and thermoplastic polyurethane exhibit different Young's moduli at different temperatures. By increasing the temperature, their Young's moduli can be reduced to change their maximum value of force. Thus, without changing the applied external force, the relationship between the applied external force and the maximum value (or critical value) of the force of the fifth elastic element 13 can be adjusted to achieve the conversion between the third and fourth conditions.

[0101] In one embodiment of the present invention, the fourth elastic element 12 and the sixth elastic element 14 are both elastic elements made of positive stiffness material; preferably, the fourth elastic element 12 and the sixth elastic element 14 are both tension springs.

[0102] In one embodiment of the present invention, the first limiting member 15 and the second limiting member 16 are both rigid material limiting members, both are rigid structures, and have a limiting function.

[0103] It should be understood that the variable stiffness tension system in the above embodiments can be a two-dimensional structure or a three-dimensional structure.

[0104] The preparation method of the variable stiffness support system and variable stiffness tension system based on the above embodiments includes the following steps:

[0105] Using 3D printing technology, a variable stiffness support system or a variable stiffness tension system as described in the above embodiments of the present invention can be printed as a whole; or, multiple substrates, multiple elastic elements, and multiple limiting elements of a variable stiffness support system or a variable stiffness tension system as described in the above embodiments of the present invention can be prepared separately and then assembled.

[0106] Specifically, the variable stiffness support system or variable stiffness tension system in the above embodiments of the present invention is realized by 3D printing technology. It can be printed as a whole according to the above structure, or each component can be prepared or printed separately and then assembled to form the variable stiffness support system or tension system. If silicone material is used, it can be cured and formed in a mold.

[0107] The present invention provides a method for preparing a variable stiffness support system or a variable stiffness tension system, which adopts technologies such as 3D printing or machining. It can directly print and manufacture the variable stiffness support system or variable stiffness tension system in the above embodiments of the present invention, or it can prepare each component separately and then assemble them. The preparation process is flexible, fast and reliable.

[0108] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A variable stiffness support system, characterized in that, include: First substrate (1); The second substrate (2) is disposed opposite to the first substrate (1); The third substrate (3) is located between the first substrate (1) and the second substrate (2); The first elastic element (5) has one end connected to the first substrate (1) and the other end connected to one end of the third substrate (3). A fourth substrate (4) is located between the first substrate (1) and the second substrate (2), and one end of the fourth substrate (4) is located between the first substrate (1) and the third substrate (3); The second elastic element (6) has one end connected to the other end of the third substrate (3) and the other end connected to one end of the fourth substrate (4). The third elastic element (7) has one end connected to the other end of the fourth substrate (4) and the other end connected to the second substrate (2); Under the first condition, there is a gap between the first substrate (1), the fourth substrate (4), the third substrate (3), and the second substrate (2); Under the second condition, the third substrate (3) is bonded to the second substrate (2), and the fourth substrate (4) is bonded to the first substrate (1).

2. The variable stiffness support system according to claim 1, characterized in that, The second elastic element (6) has a maximum force; The first condition is that the pressure between the first substrate (1) and the second substrate (2) is less than the maximum value of the force of the second elastic member (6); The second condition is that the pressure between the first substrate (1) and the second substrate (2) is greater than the maximum value of the force of the second elastic member (6).

3. The variable stiffness support system according to claim 2, characterized in that, The second elastic element (6) includes: a polylactic acid elastic element or a polyurethane elastic element; Under the first condition, by changing the temperature of the environment in which the second elastic element (6) is located, the maximum value of the force of the second elastic element (6) is reduced, thereby transforming it into the second condition; or, Under the second condition, by changing the temperature of the environment in which the second elastic element (6) is located, the maximum value of the force of the second elastic element (6) is increased, thereby transforming it into the first condition.

4. The variable stiffness support system according to any one of claims 1 to 3, characterized in that, Both the first elastic element (5) and the third elastic element (7) are elastic elements made of positive stiffness material.

5. The variable stiffness support system according to claim 4, characterized in that, Both the first elastic element (5) and the third elastic element (7) are pressure springs.

6. A tension system with variable stiffness, characterized in that, include: Fifth substrate (8); The sixth substrate (9) is disposed opposite to the fifth substrate (8); The seventh substrate (10) is located between the fifth substrate (8) and the sixth substrate (9); The fourth elastic element (12) is connected at one end to the fifth substrate (8) and at the other end to one end of the seventh substrate (10). The eighth substrate (11) is located between the fifth substrate (8) and the sixth substrate (9), and one end of the eighth substrate (11) is located between the sixth substrate (9) and the seventh substrate (10). The fifth elastic element (13) is connected at one end to the other end of the seventh substrate (10) and at the other end to one end of the eighth substrate (11). The sixth elastic element (14) has one end connected to the other end of the eighth substrate (11) and the other end connected to the sixth substrate (9). The first limiting member (15) is fixedly connected to the fifth substrate (8) and is used to limit the eighth substrate (11). The second limiting member (16) is fixedly connected to the sixth substrate (9) and is used to limit the seventh substrate (10); Under the third condition, there is a gap between the first limiting member (15) and the eighth substrate (11), and a gap between the second limiting member (16) and the seventh substrate (10). Under the fourth condition, the first limiting member (15) is attached to and limited by the eighth substrate (11), and the second limiting member (16) is attached to and limited by the seventh substrate (10).

7. The variable stiffness tension system according to claim 6, characterized in that, The fifth elastic element (13) has a maximum force value; The third condition is that the tensile force between the fifth substrate (8) and the sixth substrate (9) is less than the maximum value of the force of the fifth elastic member (13); The fourth condition is that the tensile force between the fifth substrate (8) and the sixth substrate (9) is greater than the maximum value of the force of the fifth elastic member (13).

8. The variable stiffness tension system according to claim 7, characterized in that, The fifth elastic element (13) includes: a polylactic acid elastic element or a polyurethane elastic element; Under the third condition, by changing the temperature of the environment in which the fifth elastic element (13) is located, the maximum value of the force of the fifth elastic element (13) is reduced, thereby transforming into the fourth condition; or, Under the fourth condition, by changing the temperature of the environment in which the fifth elastic element (13) is located, the maximum value of the force of the fifth elastic element (13) is increased, thereby transforming it into the third condition.

9. The variable stiffness tension system according to any one of claims 6 to 8, characterized in that, Both the fourth elastic element (12) and the sixth elastic element (14) are elastic elements made of positive stiffness material.

10. The variable stiffness tension system according to claim 9, characterized in that, Both the first limiting member (15) and the second limiting member (16) are rigid material limiting members.

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