92 results about "Creep strain" patented technology

The invention relates to a high temperature creep life accelerated test method of a material, which comprises: a plurality of groups of short time stress relaxation tests of the material at the same temperature, acquiring a relaxation rate-stress curve based on the numerical differentiation principle, forming a relaxation creep rate-stress curve by utilizing a relaxation equation, calculating creep data to build a creep curve, and building a steady state creep rate curve and a Norton creep equation. The method starts from the physical relation between relaxation and creep, covers rather broad properties of creep strain rate by utilizing the short time relaxation process, and educes broader creep data than that educed from general creep tests by above ten times, thereby effectively reducing the amount of high temperature creep tests and time of tests and providing basic data for development of new material and engineering application.

The invention discloses a method for predicting the fatigue life of a lead-free solder joint in electronic packaging, which belongs to the technology of materials science and engineering application. How to effectively predict the service life of the lead-free solder joints of an electronic packaging structure attracts great attention of enterprises. The method for predicting the fatigue life of the lead-free solder joint in electronic packaging comprises the following steps: (1) obtaining the performance parameter of the material of each part of an electronic packaging device, and determining a constitutive model of the solder joint; (2) establishing a three-dimensional finite element model according to the researched structure of the electronic packaging device, and adding boundary conditions and corresponding loads according to the actual service conditions to perform value analogue analysis; and (3) analyzing the solder joint reliability and predicting the service life. The invention has the advantages of reasonably considering the coupling effect of plastic strain and creep strain generated by the same mechanism, thus greatly improving the precision and reliability of the service life prediction result, while ensuring simple prediction method and shortening the product development period.

The invention discloses a safety evaluation method for the shortcomings of a high temperature production device or part, comprising the steps as follows: a creep strain-time curve of the material of the high temperature production device or part at a particular temperature is obtained, and an isochronous stress-strain curve corresponding to the particular time is established based on the creep strain-time curve; a failure assessment curve chart related to time is established; and a parameter Kr which can determine and reflect the cracking failure degree of the part and a parameter Lr which can determine and reflect the ultimate load failure degree of the part are counted; and finally the parameters(Kr and Lr) are put into the failure assessment chart as state points for comparing so as to determine the failure assessment point and judge the safety of the failure assessment point. The method can be used for analyzing the safety of the shortcomings during the production process and the use process of the high temperature production device or part, thereby avoiding unnecessary maintenance and premium, and further increasing the rationality of making maintenance plans for high temperature production devices.

Unique thermoplastic (polypropylene, specifically) monofilament and/or tape fibers and yarns that exhibit heretofore unattained physical properties are provided. Such fibers are basically manufactured through the extrusion of thermoplastic resins that include a certain class of nucleating agent therein, and are able to be drawn at high ratios with such nucleating agents present, that the tenacity and modulus strength are much higher than other previously produced thermoplastic fibers (particularly those produced under commercial conditions), particularly those that also simultaneously exhibit extremely low shrinkage rates. Thus, such fibers require the presence of certain compounds that quickly and effectively provide rigidity to the target thermoplastic (for example, polypropylene), particularly after heat-setting. Generally, these compounds include any structure that nucleates polymer crystals within the target thermoplastic after exposure to sufficient heat to melt the initial pelletized polymer and allowing such an oriented polymer to cool. The compounds must nucleate polymer crystals at a higher temperature than the target thermoplastic without the nucleating agent during cooling. In such a manner, the "rigidifying" nucleator compounds provide nucleation sites for thermoplastic crystal growth. The preferred "rigidifying" compounds include dibenzylidene sorbitol based compounds, as well as less preferred compounds, such as [2.2.1]heptane-bicyclodicarboxylic acid, otherwise known as HPN-68, sodium benzoate, talc, certain sodium and lithium phosphate salts [such as sodium 2,2'-methylene-bis-(4,6-di-tert-butylphenyl)phosphate, otherwise known as NA-11]. Specific methods of manufacture of such inventive thermoplastic fibers, as well as fabric articles made therefrom, are also encompassed within this invention.

The invention provides a method for forecasting the high-temperature-alloy creep life. The method includes the steps that on the basis of the theta projection method, the factor that changes of true stress are caused by changes of the material shape in the creep process is introduced, the correction theta projection method is obtained, and the concrete form is epsilon= theta1*(1-exp(theta2*(1+theta5*epsilon)*t))+theta3*(exp(theta4*(1+theta5*epsilon)*t)-1). The method can be used for forecasting a creep curve at the whole homogeneous deformation stage through initial data from the first stage to the third stage of the creep curve, and the obtaining time of creep data can be shortened. Meanwhile, the method can be used for forecasting creep curves under other creep conditions, and the forecasting process comprises forecasting of the creep rupture time under the some creep condition and the creep interruption time corresponding to some creep strain. The method is simple, reliable and suitable for different-type high temperature alloy and engineering application, and has broad prospects in the aspect of high-temperature-alloy creep life management.

The invention discloses a creep damage calculation method and model under variable load history. The method includes: acquiring the creep strain-time curve, minimum creep rate epsilon<c>m, fracture creep strain epsilon<c>f and fracture life tf of a material under different temperature and stress according to a uniaxial creep test; selecting a creep constitutive equation, and using uniaxial creep test fitting to obtain the creep constitutive parameters of the material; acquiring parameters A and B according to two simple two-stage variable load creep test data fitting; recording deformation increment generated by each stage of load according to the multi-stage variable load creep test of the material; calculating creep damaged generated of the n-1 stage before the multi-stage variable loadcreep test of the material; according to the variable load creep damage calculation model, if the acting time of the nth-stage load is known, predicting the deformation of the material under the nth-stage load, and if the nth-stage load is loaded until fracture occurs, predicting the acting time of the nth-stage load. The method can precisely consider the loading history.

The invention discloses an epoxy resin structural adhesive and a preparation method thereof, belonging to the technical filed of chemical adhesive preparation. The used raw material consists of a resin system, an adhesive component A and a curing agent system component B, and the component A and component B are completely mixed and then cured at room temperature. The structural adhesive in the invention has the advantages of high strength and toughness, good creep resistance, little creep strain, good fatigue resistance and shock resistance, good heat resistance, medium resistance and corrosion resistance, particularly good muggy and aging resistance, excellent creep rupture strength, enough safety and reliability, good flame retardant property, low stress, high strength, high adhesive force, high reliability and the like, and complies with environmental requirements. The epoxy resin structural adhesive is mainly used for adhering composite materials, such as manufacturing yachts, building houses with composite boards, adhering and manufacturing containers made of large-scale composite materials, and the like.

An electronic isolation shield mounts on a circuit board, around an electronic component to provide a minimum amount of shielding over a set period of time. The shield has a body made from a shielding material that is sized and shaped to fit around and cover the electronic component. The body has a sealing edge that is adapted to contact an upper surface of the circuit board and surround the electronic component. Resilient downwardly projecting tabs are attached to the body and each includes a securing end that extends past the sealing edge. The tab is securable to the circuit board along a securing axis. The sealing edge of the body is forced into sealing engagement with the upper surface of circuit board. The tab is laterally displaced with respect to the securing axis continuously over the set period of time so that the sealing edge is forced into the circuit board sufficiently to provide the minimum amount of shielding to the electronic component over the set period of time. A method of determining the minimum number of tabs that are required includes ascertaining the creep strain for the tab material, determining the mathematical ratio between pressure applied by the tabs at the beginning of the shield's service life to the pressure applied at the end of the service life, determining the minimum amount of pressure that is required to be applied by the tabs throughout the service life, and determining the minimum number of tabs that are required to apply the determined minimum pressure throughout the entire set period of time based on the determined mathematical ratio.

A linear object is composed of a magnesium alloy including, in percent by mass, 0.1% to 6% of Zn, 0.4% to 4% of Ca, and the balance being Mg and incidental impurities, in which, when a creep test is performed on the linear object under conditions of a temperature of 150° C., a stress of 75 MPa, and a holding time of 100 hours, the linear object has a creep strain of 1.0% or less. Zn and Ca interact with each other to improve heat resistance, and thus it is possible to obtain the linear object having an excellent creep property. By incorporating Zn and Ca, in amounts in specific ranges, into the magnesium alloy, it is also possible to obtain the linear object having excellent plastic workability.

There is provided a linear object comprising magnesium-alloy having not only excellent heat resistance but also excellent plastic formability. The linear object comprising magnesium-alloy contains, on a mass percent basis, 0.1% to 6% Y, one or more elements selected from the group consisting of 0.1% to 6% Al, 0.01% to 2% Zn, 0.01% to 2% Mn, 0.1% to 6% Sn, 0.01% to 2% Ca, 0.01% to 2% Si, 0.01% to 2% Zr, and 0.01% to 2% Nd, and the balance being Mg and incidental impurities, in which the linear object comprising magnesium-alloy has a creep strain of 1.0% or less, the creep strain being determined by a creep test at a temperature of 150° C. and a stress of 75 MPa for 100 hours.

The invention relates to the technical field of bridge engineering, in particular to a concrete creep effect analysis method. The method comprises the following steps that 1, a time-dependent concrete stress value sigma (t) is measured; 2, according to the time-dependent concrete stress value sigma (t) measured in the step 1, a time(t)-dependent variation curve graph is obtained; 3, a recurrence method is adopted for obtaining a creep strain increment; 4, according to a stress relaxation coefficient R(t, tau)=sigma(t)/sigma0, the curve graph obtained in the step 2 and the step 3, a stress value sigma 0 of the moment tau 0 of concrete is set to be equal to 1, and a computational formula of a stress relaxation coefficient R(t, tau) at the time t is obtained, wherein the equation of the computational formula is shown in the description; 5, according to the stress relaxation coefficient R(t, tau), a concrete time-dependent elasticity modulus E(t, t0) is obtained; 6, according to the computational formula of the stress relaxation coefficient R(t, tau) and the elasticity modulus E(t, t0), concrete creep effect analysis is completed. According to the analysis method, the stress-strain algebraic equation is adopted, computation is greatly simplified, and programming computational analysis is promoted.

A sawn timber drying stress evaluating method for timber quality control is disclosed. The invention relates to a sawn timber drying stress evaluating method, and solves the problem that the drying stress and residual stress detection and analysis technology in a timber drying process in the prior art are low in precision, and that the purposes of controlling drying quality and shortening drying period can not be achieved. In order to test visco elastic creep along a sheet material width direction and free drying shrinkage strain of small dimension test pieces of same tree species under drying conditions, the mechano-sorptive creep strain along the sheet material width direction is calculated based on timber drying rheology principles. Timber drying mechano-sorptive creep gradient is defined, and affecting mechanism of timber mechano-sorptive creep gradient, timber water content gradient and other parameters on sheet material drying stress releasing process is determined. Technical ambiguity of describing timber drying stress by using conventional fork-tooth microtomy can be eliminated. The method is applicable to quantified description of coniferous wood drying stress, and scientific evaluation of timber drying quality is realized. The method is applied in the timber processing technical field.

The invention discloses a pile foundation soaking load test method based on creep-strain separation, which comprises the steps as follows: firstly, a constant load is loaded; secondly, strain values of a pile body and internal force of the pile body before the soaking are tested, that is, when the settlement of a test pile is stabilized, the strain values in different depth positions of the pile body of the test pile are tested and the internal force in different depth positions of the pile body of the test pile before the soaking are analyzed; thirdly, the soaking is conducted and the strain values of the pile body during the soaking are tested, that is, when the settlement of the test pile is stabilized, the test pile is soaked, and after the test pile is soaked, the strain values in different depth positions of the pile body of the test pile are tested at regular intervals of Delta t; fourthly, an actually measured creep degree function of a calibration section is obtained; fifthly, the creep degree function during each loading age is obtained; and sixthly, the strain values of the pile body and the internal force of the pile body are calculated after creep separation during the soaking. The method disclosed by the invention has the advantages that the steps are simple, the testing is convenient, creep and strain can be separated from a pile body strain test result simply, conveniently, rapidly and accurately, so that the test result approximates to the practical stress state of the pile body as much as possible.

The invention discloses a large-scale foundation pit support body deformation automation analysis system and a data analysis method thereof and belongs to the foundation pit engineering field. A foundation pit support body is a reinforced concrete beam. A support body model, which has a same cross section, same reinforcement and a same concrete proportion with the foundation pit support body and is simultaneously poured, is arranged in a construction site. A data monitoring analysis system comprises a first reinforcement meter, a first concrete strain meter, a second reinforcement meter, a second concrete strain meter and an intelligent monitoring platform. The intelligent monitoring platform can correspondingly decompose a stress and strain of the monitored foundation pit support body into data of a load stress, a temperature stress, a contraction stress, load strain, temperature strain, contraction strain, creep strain and the like through using each monitored data. In the technical scheme of the invention, a stress condition of the foundation pit support body can be accurately grasped so that safety guarantee is provided for foundation pit construction.

A system and methods for lifing a single crystal turbine blade of a gas turbine engine is disclosed. The system and methods determine the anisotropic strain of the single crystal turbine blade caused by fatigue and creep by resolving the shear stresses on each of the primary slip systems of the single crystal turbine blade. The system and methods use a ductility exhaustion method to combine the anisotropic fatigue and creep strains to determine the operating life of the single crystal turbine blade.

The invention belongs to the technical field of coal mine freezing method vertical shaft sinking simulation, particularly relates to a coal mine vertical shaft freezing sinking process simulation calculation method. The method comprises the following two steps of 1, carrying out rock creep test, coring a frozen wall of a vertical shaft to be simulated, processing the frozen wall into a cylindricalrock sample with the diameter of 50mm and the height of 100mm, carrying out rock uniaxial creep tests at different temperatures to obtain a change rule of creep strain of the rock sample along with time in different temperature states, and calculating a rock creep constitutive equation at different temperatures according to the change rule; and 2, establishing a vertical shaft sinking model, embedding the creep constitutive equation obtained in the step 1 in finite element simulation software under different temperature states, setting temperature change and control time, and simulating the whole vertical shaft sinking process through the established model. According to the method, the stress deformation condition of the stratum confining pressure in each construction stage of freezing method sinking is simulated and calculated according to the actual influence of the creep deformation of the frozen wall, and the calculation result can guide the actual construction guidance.

A design method for reinforcing railway karst roadbed with high-strength geotextiles is provided, in order to solve the problem of lack of the theoretical basis and the design method when using high-strength geotextiles to reinforce the railway karst roadbed in actual design. The method is performed as the following steps: determining the size of the cavern and the upper load of the high-strengthgeotextile; determining the permissible value of the road surface deformation and the long-term strain and the creep strain tolerance of the high-strength geotextile; determining the ultimate strength, the short-term tension-strain relationship, and the long-term used tension-strain relationship of the high-strength geotextile; calculating the tension and the corresponding strain when the high-strength geotextile reaches the equilibrium position; calculating the deformation of the roadbed surface caused by deformation of the high-strength geotextile; calculating the long-term strain and the creep strain of the high-strength geotextile; and calculating the anchorage segment length to complete the design process.

A rotor life estimation device of a vacuum pump including a rotor rotatably driven by a motor and a rotor temperature detection section configured to detect a temperature of the rotor, comprises: an arithmetic section configured to calculate a strain equivalent corresponding to creep strain of the rotor based on a correlation between a creep strain speed equivalent and the temperature of the rotor and the temperature detected by the rotor temperature detection section; an estimation section configured to estimate a rotor life based on the calculated strain equivalent; and a providing section configured to provide information on the estimated rotor life.