Elongmeter structure with spaced flexure

Abstract

An extensometer structure includes: a flexure assembly having a support mount; a first contact device mount rigidly fixed to the support mount; and a second contact device mount coupled to the support mount through an upper flexure arm and a lower flexure arm. The upper flexure arm is spaced apart from and disposed directly above and aligned with the lower flexure arm. The second contact device mount is configured to travel vertically relative to the first contact device mount.

Description

Background Art

[0001] The following discussion is provided for general background information only and is not intended to be used as an aid in determining the scope of the claimed subject matter.

[0002] Extensometers are commonly used to measure strain on a test specimen. Various forms of extensometers have been proposed in the art. One type of extensometer is a contact extensometer that contacts a test specimen being loaded to determine the specimen's properties. Strain is sensed by contact probes that engage the specimen at a contact point and extend through a flexure assembly to a sensor system support. The flexure assembly enables the probes to move relative to each other to measure strain on the test specimen. Summary of the invention

[0003] This Summary is provided to introduce selected concepts in a simplified form that are further described below in the Detailed Description. This Summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used as an aid in determining the scope of the claimed subject matter.

[0004] An extensometer structure includes: a flexure assembly having a support mount; a first contact device mount rigidly fixed to the support mount; and a second contact device mount coupled to the support mount by an upper flexure arm and a lower flexure arm. The upper flexure arm is spaced from the lower flexure arm and disposed directly above and aligned with the lower flexure arm. The second contact device mount is configured to travel vertically relative to the first contact device mount.

[0005] The extensometer structure may include a first contact probe and a second contact probe, wherein the first contact probe has a contact surface and is fastened to a first contact device mounting seat, and the second contact probe has a contact surface and is fastened to a second contact device mounting seat, wherein the second contact probe is configured to travel vertically in a substantially parallel manner relative to the first contact probe.

[0006] The first contact probe and the second contact probe include a first slender rod and a second slender rod, wherein the first slender rod is mounted to the first contact device mounting seat and extends from the contact surface along the lower side of the first contact device mounting seat and the lower side of the support mounting seat and terminates at the proximal end, and wherein the second slender rod is mounted to the second contact device mounting seat and extends from the contact surface through the slot on the second contact device mounting seat, extends between the upper flexure arm and the lower flexure arm and passes through the slot on the support mounting seat to reach the proximal end.

[0007] The first contact probe and the second contact probe may include a first blade-like blade and a second blade-like blade, wherein the first blade-like blade mounting seat is mounted to the front end and underside of the first contact device mounting seat, and the second blade-like blade is clamped into a groove recessed from the front of the second contact device mounting seat.

[0008] The flexure assembly may further include at least one overtravel stop. The at least one overtravel stop may include a first overtravel stop and a second overtravel stop, the first overtravel stop being mounted to the first contact device mounting seat and having a first flange, the first flange having a free end that moves within a first groove recessed in the second contact device mounting seat, and the second overtravel stop being mounted to the first contact device mounting seat and having a second flange, the second flange having a free end that moves within a second groove recessed in the second contact device mounting seat. The first overtravel stop and the second overtravel stop provide a limited travel of the second contact device mounting seat relative to the first contact device mounting seat.

[0009] The upper flexure arm may include a first flexure zone, a second flexure zone, and a rigid interconnecting section coupling the first flexure zone to the second flexure zone, and wherein the lower flexure arm may include a first flexure zone, a second flexure zone, and a rigid interconnecting section coupling the first flexure zone to the second flexure zone.

[0010] The extensometer structure may include one or more sensors configured to sense movement of the second contact device mount relative to the first contact device mount. For example, the one or more sensors may include four strain gauge sensors, wherein the first strain gauge sensor and the second strain gauge sensor are positioned on the upper flexure arm, and wherein the third strain gauge sensor and the fourth strain gauge sensor are positioned on the lower flexure arm. In another embodiment, the one or more sensors may include eight strain gauge sensors, wherein the first strain gauge sensor, the second strain gauge sensor, the third strain gauge sensor, and the fourth strain gauge sensor are positioned on the upper surface and the lower surface of the upper flexure arm, and wherein the fifth strain gauge sensor, the sixth strain gauge sensor, the seventh strain gauge sensor, and the eighth strain gauge sensor are positioned on the upper surface and the lower surface of the lower flexure arm.

[0011] An extensometer structure includes: a first contact probe having a contact surface; a second contact probe having a contact surface and movably connected to the first contact probe; and a flexure assembly. The flexure assembly includes a support mount, a first contact device mount, the first contact device mount being rigidly fixed to the support mount and configured to support the first contact probe. The first contact probe is mounted to the first contact device mount. The second contact device mount is coupled to the support mount by an upper flexure arm and a lower flexure arm. The second contact probe is mounted to the second contact device mount. The second contact device mount is configured to travel vertically relative to the first contact device mount, and wherein the second contact probe is configured to travel vertically relative to the first contact probe.

[0012] The first contact probe and the second contact probe may include a first slender rod and a second slender rod, wherein the first slender rod is mounted to the first contact device mounting seat and extends from the contact surface of the first slender rod along the lower side of the first contact device mounting seat and the lower side of the support mounting seat and terminates at the proximal end, and wherein the second slender rod is mounted to the second contact device mounting seat and extends from the contact surface of the second slender rod through the slot on the second contact device mounting seat, extends between the upper flexure arm and the lower flexure arm and passes through the slot on the support mounting seat to reach the proximal end. The flexure assembly may further include at least one overtravel stop. Moreover, the upper flexure arm may be spaced apart from the lower flexure arm and arranged directly above the lower flexure arm and aligned with the lower flexure arm.

[0013] The upper flexure arm may include a first flexure zone, a second flexure zone, and an interconnecting section coupling the first flexure zone to the second flexure zone, and wherein the lower flexure arm may include a first flexure zone, a second flexure zone, and an interconnecting section coupling the first flexure zone to the second flexure zone.

[0014] One or more sensors may be configured to sense movement of the second contact device mount relative to the first contact device mount, wherein the one or more sensors are positioned on the upper flexure arm and the lower flexure arm. The one or more sensors may be positioned on the upper flexure arm and the lower flexure arm.

[0015] An extensometer assembly includes an extensometer structure having a first elongated rod extending from a contact surface to a proximal end, a second elongated rod extending from the contact surface to the proximal end, and a flexure assembly having at least one flexure arm. The flexure assembly includes a support mount, a first contact device mount rigidly fixed to the support mount, and a second contact device mount coupled to the support mount by at least one flexure arm. The first elongated rod is mounted to the first contact device mount, and the second elongated rod is mounted to the second contact device mount. The extensometer assembly further includes a clamping system coupled to the proximal ends of the first elongated rod and the second elongated rod to provide a lifting force and a contact force.

[0016] The at least one flexure arm may include an upper flexure arm and a lower flexure arm, the upper flexure arm being spaced apart from and aligned with the lower flexure arm.

[0017] The first slender rod can extend from the contact surface of the first slender rod along the lower side of the first contact device mounting seat and the lower side of the support mounting seat, and terminate at the proximal end of the first slender rod, and the second slender rod can extend from the contact surface of the second slender rod through the slot on the second contact device mounting seat, extend between the upper flexure arm and the lower flexure arm and through the slot on the support mounting seat to reach the proximal end of the second slender rod.

[0018] One or more sensors may be configured to sense movement of the second contact device mount relative to the first contact device mount, wherein the one or more sensors are positioned on the upper flexure arm and the lower flexure arm. The one or more sensors may be positioned on the upper flexure arm and the lower flexure arm. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 is a front perspective view of an extensometer according to an embodiment.

[0020] Figure 2 yes Figure 1 Rear perspective view of the extensometer shown.

[0021] Figure 3 yes Figure 1 and Figure 2 A top front perspective view of the extensometer structure of the extensometer is shown.

[0022] Figure 4 yes Figure 3 A top-down perspective view of the .

[0023] Figure 5 yes Figure 3 A top-down stereogram of the .

[0024] Figure 6 yes Figure 3 Front view of.

[0025] Figure 7 is along Figure 6 A top front perspective sectional view taken along the section line shown in FIG.

[0026] Figure 8 is a top front perspective view of a sensing assembly according to an embodiment, the sensing assembly being configured for Figure 1 and Figure 2 The extensometer shown is used and includes Figure 3 The extensometer structure shown.

[0027] Fig. 9 yes Figure 8 A bottom perspective view of a portion of the sensing assembly is shown.

[0028] Fig.10 yes Fig. 9 A schematic diagram of a portion of the sensing assembly is shown.

[0029] Fig.11 is with Fig.10 Schematic diagram of the sensing circuit corresponding to the sensing component shown.

[0030] Fig.12 is a top front perspective view of a sensing assembly according to another embodiment, the sensing assembly being configured for use in Figure 1 and Figure 2 Shown include Figure 3 The extensometer structure shown is used in the extensometer.

[0031] Fig.13 yes Fig.12 A bottom perspective view of a portion of the sensing assembly is shown.

[0032] Fig.14 yes Fig.12 Schematic diagram of the sensing component.

[0033] Fig.15 is with Fig.14 Schematic diagram of the sensing circuit corresponding to the sensing component shown.

[0034] Fig.16 According to the embodiment Figure 3 The extensometer structure and Figure 1 and Figure 2 A top rear perspective view of the rear assembly of the extensometer is shown.

[0035] Fig.17 yes Fig.16 A top and side perspective view of .

[0036] Fig.18 yes Fig.16 and Fig.17 A top front perspective view of the extensometer structure and hold-down system of the extensometer is shown.

[0037] Fig.19 yes Fig.18 Rear view of.

[0038] Fig. 20 is along Fig.18 A cross-sectional view taken along the section line shown.

[0039] Fig.21 is a top perspective view of an extensometer structure of an extensometer according to another embodiment. DETAILED DESCRIPTION

[0040] Contact extensometers measure deformation of a sample specimen by placing contact probes, such as but not limited to the end of an elongated ceramic rod or a knife-edge blade, directly onto the specimen and coupling these contact probes to a flexure assembly to allow at least one of the contact probes to move in response to compression or extension of the test specimen. Figure 1 is a front perspective view of a contact extensometer assembly 100 according to an embodiment. Figure 21 is a rear perspective view of a contact extensometer assembly 100. The extensometer assembly 100 is one embodiment of an exemplary high temperature extensometer assembly configured to measure axial strain in high temperature tension, compression, and through-zero fatigue testing applications, such as, but not limited to, 2200 degrees Fahrenheit. The contact extensometer assembly 100 senses strain by having exemplary first and second contact probes or elongated rods 102 and 104 made of, for example, ceramic, engaging the specimen at contact points or surfaces located at distal ends 106 and 108 of the respective rods 102 and 104. The rods 102 and 104 extend to a rear assembly 110 that is away from the high temperatures and shielded from the high temperatures by a shield 112. The rear assembly 110 provides contact force on the specimen and provides lifting support on the rods 102 and 104.

[0041] The extensometer assembly 100 includes an extensometer structure 114, and in one embodiment, has a first lower elongated rod 102, a second upper elongated rod 104, and a flexure assembly 116. As used herein, an "extensometer structure" is defined as at least some of the interconnected mechanical components and does not include any sensing devices for measuring movement of the components of the extensometer structure. Rather, various types of sensing devices that are well known may be used with the extensometer structure disclosed herein to form an operable extensometer that provides an output signal indicative of displacement, such as elongation of a specimen.

[0042] As described, the extensometer structure 114 is supported by the rear assembly 110, which includes a hold-down system 120 configured to apply a contact force on the specimen through the extensometer structure 114 and to provide a lifting force to the extensometer structure 114. Figure 2 As shown, the clamping system 120 includes a support bridge 122, which is connected to a lower flexible bridge 124 and an upper flexible bridge 126. The lower flexible bridge 124 is connected to the proximal end ( Figure 1 and Figure 2 ), and the upper flexible bridge 126 is connected to the proximal end of the second elongated rod 104 ( Figure 1 and Figure 2 10). In this embodiment, the extensometer structure 114 provides the contact force on the test specimen through the rods 102 and 104. The rear assembly 110 will be discussed in more detail below.

[0043] Figure 3 yes Figure 1 and Figure 2 A top front perspective view of the extensometer structure 114 is shown. Figure 4 This is a three-dimensional picture from top view. Figure 5 is a stereogram viewed from above, and Figure 6 yes Figure 3 Front view of. Figure 7 is along Figure 6 The flexure assembly 116 features of the extensometer structure 114 act as a compliant spring and enable the second elongated rod 104 to move vertically in a substantially parallel manner relative to the first elongated rod 102 when in contact with the specimen.

[0044] The flexure assembly 116 includes a first contact device mount 128 extending from the front to the rear of the flexure assembly 116 to the support mount 136, and a second contact device mount 130 coupled to the support mount 136 via an upper flexure arm 160 and a lower flexure arm 162. The second contact device mount 130 moves vertically relative to the first contact device mount 128 by flexing the flexure arms 160, 162. Figure 5 As shown, the rear portion of the first contact device mount 128 can be rigidly secured to the support mount 136, such as by fasteners (such as a pair of mechanical fasteners 138 and 139), adhesives, welding, etc., or formed as a single unit with the flexure assembly 116.

[0045] If desired, an overtravel stop may be provided to limit the range of movement of the second contact device mount 130 relative to the first contact device mount 128. Typically, the overtravel stop allows the second contact device mount 130 to move freely, with its movement limited by surface contact that prevents further movement. In the illustrated embodiment, the overtravel stop includes a pair of first and second overtravel stops 132 and 134. The overtravel stops 132 and 134 are both fixed to the front of the first contact device mount 128 and opposite sides of the first contact device mount 128, and include a first flange 140 and a second flange 142. As shown, the overtravel stops 132 and 134 can be rigidly fixed to both sides of the first contact device mount by mechanical fasteners 133 and 135.

[0046] The second contact device mount 130 is configured to travel vertically relative to the first contact device mount 128 and the rear support mount 136 and includes a pair of first grooves 144 and second grooves 146 recessed into the second contact device mount 130. The grooves 144 and 146 are configured to receive the free ends of the first flange 140 and the second flange 142. The first groove 144 is located on a first side of the mount 130, and the free end of the first flange 140 moves within the first groove 144. The second groove 146 is located on a second, opposite side of the mount 130, and the free end of the second flange 142 moves within the second groove 146. In this way, the grooves 144 and 146 define the distance to which the second contact device mount 130 can move relative to the first contact device mount 128, and thereby accommodate the tensile and compressive travel allowances on either side of the second contact device mount 130. Figure 6This relative distance is best illustrated by showing the spacing distance between the top of the flanges 140 and 142 and the top of the grooves 144 and 146, and the spacing distance between the bottom of the flanges 140 and 142 and the bottom of the grooves 144 and 146. In other words, the over-travel stops 132 and 134, in combination with the grooves 144 and 146, respectively, provide limited travel of the second contact device mount 130 relative to the first contact device mount 128. In addition, the over-travel stops 132 and 134 limit lateral movement of the second contact device mount 130 relative to the first contact device mount 128, and therefore limit lateral movement of the flexure arms 160 and 162 due to, for example, side-to-side movement and / or twisting of the first and second elongated rods 102 and 104.

[0047] The first and second elongated rods 102 and 104 are coupled to the flexure assembly 116. As shown, the first elongated rod 102 is fixed and extends from the contact device end 106 to the proximal end 148. The second elongated rod 104 is configured to move or shift upward and downward in a substantially parallel manner relative to the fixed first elongated rod 102 and extends from the contact device end 108 to the proximal end 150. The first elongated rod 102 is fixed by being rigidly fixed to the underside of the first contact device mount 128 along a channel 129 that is recessed into a portion of the bottom surface of the first contact device mount 128. At the front of the first contact device mount 128, a rod support block 152 is used to retain the first elongated rod 102 in the channel 129 of the first contact device mount 128, and the rod support block includes its own channel for retaining the rod 102. For example and as shown, the rod support block 152 may rigidly secure the first elongated rod 102 to the first contact device mount 128 using mechanical fasteners 153 and 154 .

[0048] The second elongated rod 104 extends through the slot 131 on the second contact device mount 130 and through the slot 137 on the support mount 136. Although the second elongated rod 104 can move within the slot 137 of the support mount 136, the second elongated rod 104 is fixed in the slot 131 of the movable second contact device mount 130. In the illustrated embodiment, the V-block 156 and the set screw 158 (such as Figure 5 , Figure 6 and Figure 7 ) provides a compressive or clamping force to the second elongated rod 104. Thus, the second elongated rod 104 is configured to travel vertically with the second contact device mount 130 in a substantially parallel manner relative to the first elongated rod 102 rigidly mounted to the first contact device mount 128.

[0049] Although the flexure assembly 116 further includes an upper flexure arm 160 and a lower flexure arm 162, the flexure assembly 116 may also include one flexure arm. As shown, the second contact device mounting seat 130 is connected to the support mounting seat 136 by the upper flexure arm 160 and the lower flexure arm 162. The flexure arms 160 and 162 are spaced apart and aligned with each other, and the upper flexure arm 160 is arranged directly above the lower flexure arm 162. In the illustrated embodiment, the longitudinal axis 160A along the center line of the upper flexure arm 160 is substantially aligned with the longitudinal axis 162A along the center line of the lower flexure arm 162. Preferably, the longitudinal axes 160A and 162A are also substantially aligned with the longitudinal axes of the rods 102 and 104. Both the upper flexure arm 160 and the lower flexure arm 162 are connected to the second contact device mounting seat 130 at the front end and connected to the support mounting seat 136 at the rear end. Additionally, the upper flexure arm 160 is located above the second elongated rod 104, and the lower flexure arm 162 is located below the second elongated rod 104. In one embodiment, the second contact device mount 130, the rear support mount 136, the upper flexure arm 160, and the lower flexure arm 162 can all be made integrally, or formed from a single unitary body.

[0050] The upper flexure arm 160 and the lower flexure arm 162 enable the second elongated rod 104 to travel in response to compression or extension of the test specimen and handle the moments generated by the contact forces or shear forces at the contact surfaces 106 and 108 of the rods 102 and 104. The upper flexure arm 160 includes a first flexure zone 164, a second flexure zone 166, and a rigid interconnecting section 168 that couples the first flexure zone 164 to the second flexure zone 166. The lower flexure arm 162 includes a first flexure zone 170, a second flexure zone 172, and a rigid interconnecting section 174 that couples the first flexure zone 170 to the second flexure zone 172. Although Figures 1 to 7 The upper and lower flexure arms 160 and 162 are shown with two flexure bands connected by a rigid interconnecting section, but other variations are possible, including a single flexure band or more than two flexure bands with interconnecting sections. One purpose of the length of each of the upper and lower flexure arms 160 and 162 is to position the rear assembly 110 as far away from the shield 112 as possible by extending the length of the flexure assembly 116 and the length of the rods 102 and 104. In this way, the operator can be easily assembled. In addition, the flexure assembly 116 includes thin flexure bands 164, 166, 170 and 172, which makes the weight of the flexure assembly as light as possible by eliminating excessive joints held together by heavier mechanical fasteners.

[0051] In some embodiments, the flexure arms 160 and 162 are provided with Figures 1 to 7One or more strain sensor gauges, not shown, are used to sense movement of the second elongated rod 104 relative to the first elongated rod 102 or movement of the second contact device mounting base 130 relative to the first contact device mounting base 128. In other embodiments, other forms of sensors sense movement of the rod 104 relative to the rod 102. For example, sensors based on changes in capacitance, inductance, or resistance can be used. Similarly, optical-based sensors can be used if desired. Such sensing devices are well known. The aspects disclosed herein do not depend on the type of sensor or sensing device used; however, strain sensor gauges will be described.

[0052] Figure 8 is a top front perspective view of a sensing assembly 180 configured for use in the extensometer assembly 100 and, therefore, in the extensometer structure 114, according to an embodiment. Fig. 9 is a bottom perspective view of a portion of the sensing assembly 180, and Fig.10 yes Fig. 9 A schematic diagram of a portion of the sensing assembly 180 is shown in FIG. Figures 8 to 10 In the illustrated embodiment, four strain sensor gauges are used to sense the displacement of the second contact device mounting base 130, and thus the displacement of the second elongated rod 104. Specifically, the first strain sensor gauge 181 ( Fig.10 ) is applied to the bottom surface or outward-facing surface of the second flexure band 172 of the lower flexure arm 162 to measure the strain thereon, a second strain sensor gauge 182 is applied to the bottom surface or inward-facing surface of the second flexure band 166 of the upper flexure arm 160 to measure the strain thereon, a third strain sensor gauge 183 is applied to the top surface or inward-facing surface of the second flexure band 172 of the lower flexure arm 162 to measure the strain thereon, and a fourth strain sensor gauge 184 is applied to the top surface or outward-facing surface of the second flexure band 166 of the upper flexure arm 160 to measure the strain thereon.

[0053] Fig.11 1 is a schematic diagram of a sensing circuit 185 corresponding to the sensing assembly 180. The sensing circuit 185 is a Wheatstone bridge circuit. As shown, the Wheatstone bridge circuit has two excitation voltage terminals and two output terminals or signal terminals. As shown, strain sensor gauges 181 and 182, which generally sense strain tension, are opposite to each other, and strain sensor gauges 183 and 184, which generally sense strain compression, are opposite to each other.

[0054] Fig.12 is a top front perspective view of a sensing assembly 186 according to an embodiment, which is configured for use in the extensometer assembly 100 and therefore in the extensometer structure 114. Fig.13 is a bottom perspective view of a portion of the sensing assembly 186, and Fig.14yes Fig.14 A schematic diagram of the portion of the sensing assembly 186 shown in FIG. Figure 12 to Figure 14 In the illustrated embodiment, eight strain sensor gauges are used to sense the displacement of the second contact device mounting base 130, and thus the displacement of the second elongated rod 104. Specifically, the first strain sensor gauge 181 ( Fig.14 ) is applied to the bottom surface or outward-facing surface of the second flexure band 172 of the lower flexure arm 162 to measure the strain thereon, a second strain sensor gauge 182 is applied to the bottom surface or inward-facing surface of the second flexure band 166 of the upper flexure arm 160 to measure the strain thereon, a third strain sensor gauge 183 is applied to the top surface or inward-facing surface of the second flexure band 172 of the lower flexure arm 162 to measure the strain thereon, and a fourth strain sensor gauge 184 is applied to the top surface or outward-facing surface of the second flexure band 166 of the upper flexure arm 160 to measure the strain thereon. In addition, a fifth strain sensor gauge 187 is applied to the top surface or outward-facing surface of the first flexure zone 164 of the upper flexure arm 160 to measure the strain thereon, a sixth strain sensor gauge 188 is applied to the top surface or inward-facing surface of the first flexure zone 170 of the lower flexure arm 162 to measure the strain thereon, a seventh strain sensor gauge 189 is applied to the bottom surface or inward-facing surface of the first flexure zone 164 of the upper flexure arm 160 to measure the strain thereon, and an eighth strain sensor gauge 190 is applied to the bottom surface or inward-facing surface of the first flexure zone 170 of the lower flexure arm 162 to measure the strain thereon. Fig.14 ) is applied to the bottom or outward facing surface of the first flexure zone 170 of the lower flexure arm 162 to measure the strain thereon.

[0055] Fig.15is a schematic diagram of a sensing circuit 191 corresponding to the sensing assembly 185. The sensing circuit 191 is a Wheatstone bridge circuit. As shown, the Wheatstone bridge circuit has two excitation voltage terminals and two output terminals or signal terminals. As shown, strain sensor gauges 181 and 182 that generally sense strain tension on the second flexure bands 172 and 166 are opposite to each other, and strain sensor gauges 183 and 184 that generally sense strain compression on the second flexure bands 172 and 166 are opposite to each other, while strain sensor gauges 187 and 188 that generally sense strain tension on the first flexure bands 170 and 164 are opposite to each other, and strain sensor gauges 189 and 190 that generally sense strain compression on the first flexure bands 170 and 164 are opposite to each other. It should be recognized that other embodiments of the strain sensor gauges are possible. For example, two strain sensor gauges 181 and 187 that generally measure strain tension on the outward facing surfaces of flex straps 172 and 164 can be used opposite each other in the circuit, and two strain sensor gauges 184 and 190 that generally measure strain compression on the outward facing surfaces of flex straps 166 and 170 can be used opposite each other in the circuit. In another example, two strain sensor gauges 182 and 188 that generally measure strain tension on the inward facing surfaces of flex straps 166 and 170 can be used opposite each other in the circuit, and two strain sensor gauges 183 and 189 that generally measure strain compression on the inward facing surfaces of flex straps 172 and 164 can be used opposite each other in the circuit.

[0056] Fig.16 is a top rear perspective view of the extensometer structure 114 and rear assembly 110 of the extensometer assembly 100, and Fig.17 yes Fig.16 As previously discussed, the extensometer structure 114 is supported by the rear assembly 110, wherein the clamping system 120 is configured to apply a contact force on the specimen through the extensometer structure 114 and provide a lifting force to the extensometer structure 114. Fig.16 and Fig.17 As shown, the clamping system 120 includes a support bridge 122 that provides support to a lower flexible bridge 124 and an upper flexible bridge 126. The lower flexible bridge 124 is coupled to the support bridge 122 via a lower bridge mount 121, and the upper flexible bridge 126 is coupled to the support bridge 122 via an upper bridge mount 123. Opposite ends of the lower flexible bridge 124 and the upper flexible bridge 126 are coupled to one of the proximal ends of the first elongated rod 102 and the second elongated rod 104. Specifically, the lower flexible bridge 124 is coupled to the first elongated rod 102 via a first proximal end mount 125, and the upper flexible bridge 126 is coupled to the second elongated rod 104 via a second proximal end mount 127.

[0057] Fig.18 yes Fig.16 and Fig.171 is a top front perspective view of a portion of the extensometer structure 114 and the hold-down system 120 of the extensometer assembly 100 shown in FIG. Fig.19 yes Fig.18 The rear view, and Fig. 20 is along Fig.19 Each of the first proximal mounting seat 125 and the second proximal mounting seat 127 includes a recess or a socket 141 and 143, respectively, which is configured to receive the proximal end of one of the elongated rods 102 and 104. Fig. 20 As shown, the recess 141 of the first proximal mount 125 is configured to receive the proximal end 148 of the first elongated rod 102, and the recess 143 of the second proximal mount 127 is configured to receive the proximal end 150 of the second elongated rod 104. The first proximal mount 125 and the second proximal mount 127 are assembled so that each recess 141 and 143 provides lifting and contact forces to the extensometer structure 114 via the first elongated rod 102 and the second elongated rod 104, but allows the first elongated rod 103 and the second elongated rod 104 to move within the recess or socket 141 and 143. For example, the recess or socket 141 and 143 may include an opening at a 120 degree angle, and the proximal ends 148 and 150 may provide 90 degree ends. In this way, the contact of the 90 degree ends with the surface of the corresponding socket 141 and 143 is minimal, but allows any slight misalignment, but still provides the necessary lifting support force and contact force.

[0058] Fig.21 is a top front perspective view of an extensometer structure 214 according to another embodiment, the extensometer structure including a flexure assembly 216 of the contact extensometer assembly 200. Rather than the extensometer structure 214 having first and second elongated rods, the contact extensometer 200 senses strain of a specimen by having exemplary first and second knife-edge blades 202 and 204 that engage the specimen at contact points or surfaces located at distal ends 206 and 208 of the knife-edge blades 202 and 204. The features of the flexure assembly 216 of the extensometer structure 214 act as a compliant spring and enable the second knife-edge blade 204 to move vertically in a parallel manner relative to the first knife-edge blade 202 when contacting the specimen. The extensometer structure 214 is typically supported by a test specimen with a clamp and strap, as shown in U.S. Pat. No. 5,600,895, and therefore does not require a hold-down system 120.

[0059] The flexure assembly 216 includes a first contact device mount 228 extending from the front to the rear of the flexure assembly 216 to the support mount 236, and the second contact device mount 230 is connected to the support mount 236 by an upper flexure arm 260 and a lower flexure arm 262. The second contact device mount 230 moves vertically relative to the first contact device mount 228 by flexing the flexure arms 260 and 262. The rear portion of the first contact device mount 128 can be fixed, for example, by fasteners ( Fig.21 Not shown, but similar to Figure 5 The flexure assembly 216 may be rigidly secured to the support mount 136 by fasteners 138 and 139 , adhesives, welding, etc., or may be formed as a single unitary body with the flexure assembly 216 .

[0060] If desired, an overtravel stop may be provided to limit the range of movement of the second contact device mount 230 relative to the first contact device mount 228. Typically, the overtravel stop allows the second contact device mount 230 to move freely, with its movement limited by surface contact that prevents further movement. In the illustrated embodiment, the overtravel stop includes a pair of first and second overtravel stops 232 and 234. The overtravel stops 232 and 234 are each fixed to the front of the first contact device mount 128 and opposite sides of the first contact device mount 228, and include a first flange 240 and a second flange 142. As shown, the overtravel stops 232 and 234 can be secured to the first contact device mount 128 by mechanical fasteners (one of the fasteners 233 is in the Fig.21 (shown in the figure) is rigidly fixed to both sides of the first contact device mounting seat.

[0061] Additionally, overtravel stops 232 and 234 limit lateral movement of the second contact mount 230 relative to the first contact mount 128 and, therefore, limit lateral movement of the flexure arms 260 and 262 due to, for example, side-to-side movement and / or twisting of the first and second knife-edge blades 202 and 204 .

[0062] The first and second bladed blades 202 and 204 are coupled to the flexure assembly 216. As shown, the first bladed blade 202 is fixed and extends from the contact device end 206 to a proximal end (not shown). The second bladed blade 204 is configured to move or shift up and down in a substantially parallel manner relative to the fixed first bladed blade 202 and extends from the contact device end 208 to a proximal end (not shown). The first bladed blade 202 is fixed by the blade support block 252 being fixed to the underside of the first contact device mount 228. For example, the blade support block 252 can secure the first bladed blade 202 to the first contact device mount 228 using mechanical fasteners.

[0063] The second blade-type blade 204 extends into the slot 231 on the second contact device mount 230 and is compressed by the mechanical fastener acting as a clamp. Therefore, the second blade-type blade 204 is fixed in the slot 231 of the movable second contact device mount 230. In this way, the second blade-type blade 204 is configured to travel vertically with the second contact device mount 230 and travel in a substantially parallel manner relative to the first blade-type blade 102 rigidly mounted to the first contact device mount 228.

[0064] Although the flexure assembly 216 further includes an upper flexure arm 260 and a lower flexure arm 262, the flexure assembly 216 may also include one flexure arm. As shown, the second contact device mounting seat 230 is connected to the support mounting seat 236 by flexure arms 260 and 262 that are spaced apart and aligned with each other, and the upper flexure arm 260 is arranged directly above the lower flexure arm 262. Both the upper flexure arm 260 and the lower flexure arm 262 are connected to the second contact device mounting seat 230 at the front end and connected to the rear support mounting seat 236 at the rear end. The upper flexure arm 260 is spaced apart from the lower flexure arm 262 and arranged or positioned above the lower flexure arm and aligned therewith. In the illustrated embodiment, the longitudinal axis 260A along the center line of the upper flexure arm 260 is substantially aligned with the longitudinal axis 262A along the center line of the lower flexure arm 262. Preferably, the longitudinal axes 260A and 262A are also substantially aligned with the center lines of the blade-type blades 202 and 204. In one embodiment, the second contact device mount 230, the rear support mount 236, the upper flexure arm 260, and the lower flexure arm 262 may all be made of the same unitary material.

[0065] The upper flexure arm 260 and the lower flexure arm 262 enable the second blade 204 to travel in response to compression or extension of the test specimen and handle the moments generated by the contact forces or shear forces at the contact surfaces 206 and 208 of the blades 202 and 204. The upper flexure arm 260 includes a first flexure zone 264, a second flexure zone 266, and a rigid interconnecting section 268 coupling the first flexure zone 264 to the second flexure zone 266. The lower flexure arm 262 includes a first flexure zone 270, a second flexure zone 272, and a rigid interconnecting section 274 coupling the first flexure zone 270 to the second flexure zone 272. Although Fig.21The upper and lower flexure arms 260 and 262 are illustrated as having two flexure bands connected together by a rigid interconnecting section, but other variations are possible, including a single flexure band or more than two flexure bands with interconnecting sections. One purpose of the length of each of the upper and lower flexure arms 260 and 262 is to position the rear assembly, which provides both contact force and lifting force to the extensometer structure 214 so that it is far enough away from the contact surfaces 206 and 208. In this way, it can be easy for the operator to assemble. In addition, the flexure assembly 216 includes thin flexure bands 264, 266, 270 and 272, which makes the flexure assembly as light as possible by eliminating excessive joints held together by heavier mechanical fasteners.

[0066] In some embodiments, the flexure arms 260 and 262 are provided with Fig.21 One or more strain sensor gauges, not shown, may be used to sense movement of the second blade 204 relative to the first blade 102 or movement of the second contact device mount 230 relative to the first contact device mount 228. This configuration of strain sensor gauges is discussed above and described in detail in the accompanying drawings. Figures 8 to 15 . In other embodiments, other forms of sensors sense the movement of blade 104 relative to blade 102. For example, sensors based on changes in capacitance, inductance, or resistance may be used. Likewise, optical based sensors may be used if desired. Such sensing devices are well known. The aspects disclosed herein are not dependent upon the type of sensor or sensing device used, however, in embodiments where strain sensor gauges are used, the positioning of those strain sensor gauges and corresponding sensing circuitry used is important.

[0067] Although the present invention has been described with reference to preferred embodiments, workers skilled in the art will recognize that changes may be made in form and detail without departing from the spirit and scope of the invention.

Claims

1. An extensometer structure, comprising: Flexure assembly, comprising: Support mount; a first contact device mounting seat rigidly fixed to the support mounting seat; and a second contact device mount coupled to the support mount by an upper flexure arm and a lower flexure arm, wherein the upper flexure arm is spaced apart from and disposed directly above and aligned with the lower flexure arm; and Wherein, the second contact device mounting seat is configured to travel vertically relative to the first contact device mounting seat.

2. The extensometer structure of claim 1, further comprising a first contact probe having a contact surface and being secured to the first contact device mounting seat, and a second contact probe having a contact surface and being secured to the second contact device mounting seat, wherein: The second contact probe is configured to travel vertically in a substantially parallel manner relative to the first contact probe.

3. The extensometer structure of claim 2, wherein: The first contact probe and the second contact probe include a first slender rod and a second slender rod, wherein the first slender rod is mounted to the first contact device mounting seat and extends from the contact surface along the lower side of the first contact device mounting seat and the lower side of the support mounting seat and terminates at a proximal end, and wherein the second slender rod is mounted to the second contact device mounting seat and extends from the contact surface through a slot on the second contact device mounting seat, extends between the upper flexure arm and the lower flexure arm and passes through the slot on the support mounting seat to reach the proximal end.

4. The extensometer structure of claim 2, wherein: The first contact probe and the second contact probe include a first blade-type blade and a second blade-type blade, wherein the first blade-type blade is mounted to the front end and lower side of the first contact device mounting seat through a blade mounting seat, and the second blade-type blade is clamped into a groove recessed from the front of the second contact device mounting seat.

5. The extensometer structure according to any one of claims 1 to 4, wherein: The flexure assembly further includes at least one overtravel stop.

6. The extensometer structure of claim 5, wherein: The at least one overtravel stop includes a first overtravel stop and a second overtravel stop, wherein the first overtravel stop is mounted to the first contact device mounting seat and has a first flange, the first flange having a free end that moves in a first groove recessed in the second contact device mounting seat, and the second overtravel stop is mounted to the first contact device mounting seat and has a second flange, the second flange having a free end that moves in a second groove recessed in the second contact device mounting seat, wherein the first overtravel stop and the second overtravel stop provide a limited travel of the second contact device mounting seat relative to the first contact device mounting seat.

7. The extensometer structure according to any one of claims 1 to 6, wherein: The upper flexure arm includes a first flexure zone, a second flexure zone, and a rigid interconnecting section coupling the first flexure zone to the second flexure zone, and wherein the lower flexure arm includes a first flexure zone, a second flexure zone, and a rigid interconnecting section coupling the first flexure zone to the second flexure zone.

8. An extensometer structure as claimed in any one of claims 1 to 7, further comprising one or more sensors configured to sense movement of a second contact device mount relative to the first contact device mount, wherein In a first embodiment, the one or more sensors include four strain gauge sensors, wherein a first strain gauge sensor and a second strain gauge sensor are positioned on the upper flexure arm, and wherein a third strain gauge sensor and a fourth strain gauge sensor are positioned on the lower flexure arm, and wherein, in a second embodiment, the one or more sensors include eight strain gauge sensors, wherein the first strain gauge sensor, the second strain gauge sensor, the third strain gauge sensor, and the fourth strain gauge sensor are positioned on the upper and lower surfaces of the upper flexure arm, and wherein a fifth strain gauge sensor, a sixth strain gauge sensor, a seventh strain gauge sensor, and an eighth strain gauge sensor are positioned on the upper and lower surfaces of the lower flexure arm.

9. An extensometer structure, comprising: a first contact probe having a contact surface; a second contact probe having a contact surface and being movably connected to the first contact probe; Flexure assembly, comprising: Support mount; a first contact device mount rigidly fixed to the support mount and configured to support the first contact probe, the first contact probe being mounted to the first contact device mount; and a second contact device mounting seat, the second contact device mounting seat being coupled to the support mounting seat via an upper flexure arm and a lower flexure arm, the second contact probe being mounted on the second contact device mounting seat; and Wherein the second contact device mount is configured to travel vertically relative to the first contact device mount, and wherein the second contact probe is configured to travel vertically relative to the first contact probe.

10. The extensometer structure of claim 9, wherein: The first contact probe and the second contact probe include a first slender rod and a second slender rod, wherein the first slender rod is mounted to the first contact device mounting seat and extends from the contact surface of the first slender rod along the lower side of the first contact device mounting seat and the lower side of the support mounting seat and terminates at a proximal end, and wherein the second slender rod is mounted to the second contact device mounting seat and extends from the contact surface of the second slender rod through the slot on the second contact device mounting seat, extends between the upper flexure arm and the lower flexure arm and through the slot on the support mounting seat to reach the proximal end.

11. An extensometer structure according to any one of claims 9 to 10, wherein: The flexure assembly further includes at least one overtravel stop.

12. An extensometer structure according to any one of claims 9 to 11, wherein: The upper flexure arm is spaced apart from the lower flexure arm, and the upper flexure arm is arranged directly above and aligned with the lower flexure arm, and wherein, in one embodiment, the upper flexure arm includes a first flexure band, a second flexure band, and an interconnecting section connecting the first flexure band to the second flexure band, and wherein the lower flexure arm includes a first flexure band, a second flexure band, and an interconnecting section connecting the first flexure band to the second flexure band.

13. An extensometer assembly comprising: Extensometer structure, including: a first elongated rod extending from the contact surface to a proximal end; a second elongated rod extending from the contact surface to a proximal end; and a flexure assembly having at least one flexure arm and comprising a support mount, a first contact device mount rigidly secured to the support mount, and a second contact device mount coupled to the support mount by the at least one flexure arm, wherein the first elongated rod is mounted to the first contact device mount and the second elongated rod is mounted to the second contact device mount; and A clamping system is coupled to the proximal ends of the first and second elongated rods to provide a lifting force and a contact force of the first and second elongated rods on a test specimen.

14. The extensometer assembly of claim 13, wherein: The at least one flexure arm includes an upper flexure arm and a lower flexure arm, the upper flexure arm being spaced apart from and aligned with the lower flexure arm.

15. The extensometer assembly of claim 14, wherein: The first slender rod extends from the contact surface of the first slender rod along the lower side of the first contact device mounting seat and the lower side of the support mounting seat, and terminates at the proximal end of the first slender rod, and wherein the second slender rod extends from the contact surface of the second slender rod through the slot on the second contact device mounting seat, extends between the upper flexure arm and the lower flexure arm and through the slot on the support mounting seat to reach the proximal end of the second slender rod.

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