109 results about "Strain stiffening" patented technology

A polypropylene-based resin composition for injection foam molding, containing (A) 50 to 95 parts by weight of a linear polypropylene-based resin having a melt flow rate of from 10 g / 10 min. to 100 g / 10 min. and a melt tension of 2 cN or less and (B) 5 to 50 parts by weight of a modified polypropylene having a melt flow rate of from 0.1 g / 10 min. to less than 10 g / 10 min. and a melt tension of 5 cN or more and exhibiting a strain hardening property (provided that a total of the resin (A) and the resin (B) is 100 parts by weight) and a foaming agent are supplied to an injection molding machine to be injected into a die, thereby achieving a foam molding. It is thus possible to obtain a injection foamed molded article which has a satisfactory injection foam moldability, a skin layer having little silver streaks or the like on its surface, and an internal core layer having a foam of high expansion ratio and uniformly fine and a excellent appearance glossiness, lightweightness, and rigidity at a low cost.

A new class of ultra-high performance concrete with very high strength and very high tensile ductility (High Strength High Ductility Concrete) is provided that represents the culmination of two high performance cement-based composite systems, namely those of very high strength, and those of very high tensile ductility into a single composite system. The integration of high strength and ductility has been attained via the adoption of micromechanical analysis and design of fiber reinforced brittle matrix composites. In doing so, the new High Strength High Ductility Concrete material dramatically increases the energy absorption capabilities of structural systems employing this material, making it a very good candidate material where hurricanes, earthquake, impact and blast loads are a concern.

The invention provides a method for predicting high-temperature and long-term creep property of heat resistant steel, and is particularly suitable for prediction of the high-temperature and long-term creep property of 9-12% of Cr ferrite heat resistant steel. Strain hardening and strain softening behaviors of the materials in a high-temperature stretching process are obtained by a constant slow-speed and high-temperature tensile testing method at the strain rate which is smaller than or equal to 10-5S-1, so as to represent dislocation creep and predict the creep deformation behavior which is the same as the deformation mechanism. Thus, the long-term creep property of the material is estimated in advance. Compared with a creep test, the method is simple to operate, short in test period and high in efficiency, and can be used for primarily screening alloy ingredients when a new steel variety of the 9-12% of Cr ferrite heat resistant steel is designed. Compared with the traditional creep test assessment method, the design cycle of alloy is greatly shortened; and the development cost of the alloy is saved.

An in-reactor polymer blend comprises (a) a propylene-containing first polymer; and (b) an ethylene-containing second polymer such that the polymer blend comprises between about 50 wt % and about 80 wt % units derived from ethylene and between about 50 wt % and about 20 wt % units derived from propylene. The blend is substantially free of dienes and the content of ethylene in the second polymer in the form of ethylene-ethylene-ethylene triads is at least 40%. The second polymer contains at least 0.1 branch having 8 or more carbon atoms per 10,000 carbons. In addition, the blend has a strain hardening index of at least 1.8, a shear thinning slope in the plot of log(dynamic viscosity) versus log(frequency) of less than −0.2 and exhibits at least two peaks when subjected to Differential Scanning Calorimetry (first melt) corresponding to a first melting point of at least 150° C. and a second melting point of at least 40° C. such that the difference between the first and second melting temperatures is at least 20° C.

A polyethylene based resin exhibiting excellent moldability and durability and having an excellent balance between impact resistance and stiffness; and a hollow plastic molded article using the foregoing resin, which exhibits excellent moldability, durability and barrier properties and has an excellent balance between impact resistance and stiffness, are provided. The polyethylene based resin satisfies the following requirements (1) to (4): (1) a high-load melt flow rate (HLMFR) is from 1 to 100 g / 10 min; (2) a density is from 0.940 to 0.960 g / cm3; (3) a strain hardening parameter λmax of elongational viscosity is from 1.05 to 1.50; and (4) a rupture time in a full notch tensile creep test and a density satisfy the following relational expression (A): log (rupture time)≧−355×(density)+337.6 (A).

The invention discloses a method for improving elongation rate and strain hardening index n value of cold-rolled deep-drawing steel. The method comprises the steps of carrying out cold rolling by adopting a cold rolling reduction rate of 58%-77%, then carrying out cover annealing, and flattening to obtain the cold-rolled deep-drawing steel. The elongation rate of the cold-rolled deep-drawing steelis more than 40%, and the strain hardening index n value is 0.22-0.25. According to the method for improving the elongation rate and the strain hardening index n value of the cold-rolled deep-drawingsteel, through optimizing the production process method, the obtained cold-rolled deep-drawing steel has higher elongation rate and strain hardening index n value, the expansion and ductility performance of a steel plate material is improved, and the probability of fracture of the steel material in the expansion process is reduced; the production qualified rate is improved; and the method for improving the elongation rate and the strain hardening index n value of the cold-rolled deep-drawing steel is improved on the basis of an original steel production line, process parameter control is optimized, and industrial production improvement is facilitated.

The invention provides a thick plate with excellent plasticity and toughness for pipelines and a production method of the thick plate. The thick plate is prepared from components in percent by weight:0.025%-0.055% of C, 0.26%-0.40% of Si, 1.51%-1.75% of Mn, smaller than or equal to 0.010% of P, smaller than or equal to 0.0015% of S, 0.02%-0.05% of Nb, 0.010%-0.030% of Ti, 0.16%-0.35% of Cr, 0.06%-0.19% of Mo, smaller than or equal to 0.20% of Ni, smaller than or equal to 0.15% of Cu, 0.010%-0.025% of Al, 0.0010%-0.0040% of N, 0.0015%-0.0040% of Ca and the balance iron and inevitable impurities, wherein Ca / S is larger than or equal to 1.6. The production method includes the steps of converter smelting, external refining, continuous casting, heating, rolling and cooling. The thickness of the thick plate produced through the method is larger than 26 mm, and the transverse yield ratio does not exceed 0.83; and the longitudinal yield strength is 450-530 MPa, the longitudinal tensile strength is 590-670 MPa, the longitudinal uniform elongation UEL is larger than or equal to 10%, the longitudinal yield ratio does not exceed 0.82, and the strain hardening exponent n is larger than or equal to 0.1.

The invention relates to a method for quickly determining a metal material strain hardening index. The method comprises the following steps of: first, according to the tension test data, drawing a tension curve sigma-epsilon; second, determining a starting point for generating strain hardening effect; third, determining an end point for generating strain hardening effect; fourth, determining two key points: namely (epsilon1, sigma1) and (epsilon2, sigma2) on the tension curve; and fifth, according to a formula, calculating the strain hardening index. The method provided by the invention has the characteristics of easy operation, high efficiency and no influence of human factors.

The invention discloses a strip steel with the tensile strength of 440 MPa and excellent low-temperature secondary machining performance. The strip steel comprises the components of, in parts by weight, 0.0008%-0.0028% of C, 0.07%-0.1% of Si, 1.4%-1.8% of Mn, 0.06%-0.09% of P, less than or equal to 0.008% of S, 0.02%-0.05% of Al, 0.02%-0.06% of Ti, 0.006%-0.022% of Nb, 0.0005%-0.0015% of B and less than or equal to 0.002% of N. The production method comprises the following steps of smelting and casting into a blank; heating a casting blank; rough rolling; finish rolling; coiling; cold rollingafter pickling; carrying out continuous annealing treatment; slowly cooling; rapidly cooling; aging treatment; and leveling. According to the strip steel and the production method thereof, on the premise that the mechanical property is guaranteed, the plastic strain ratio is larger than or equal to 1.5 <r90>, and the strain hardening index is larger than or equal to 1.0 <n90>; and the secondary machining brittle transition temperature is stabilized below minus 50 DEG C, the amount of elements Ti and Nb is reduced, so that the cost is reduced by not less than 5%, the surface of the steel plateis free of carbonization edges and bonding defects, and therefore the steel plate can be used for preparing automobile outer covering parts applied to more severe cold areas.

The invention provides a shot peening strengthening method for controlling a strain hardening rate of a high temperature alloy surface, which comprises the following steps: 1, finding a critical strain hardening rate under a material saturated residual compressive stress field through a test; 2, determining shot peening strengthening technological parameters of the material critical strain hardening rate; and 3, utilizing the technological parameters obtained in step 2 to carry out shot peening strengthening treatment. Compared with the prior art, the technical scheme of the invention has the characteristic of low strain hardening rate, so the thermal stability of the shot peening residual compressive stress field is strong, the method is suitable for the surface peening treatment of metal parts used at a higher temperature so as to prolong the fatigue life of the metal parts and improve the fatigue resistance of the metal parts.

The invention relates to a method for precisely determining a hardening index of a material. The method comprises the following steps of: 1, drawing a tensile curve Sigma-Epsilon according to tensile test data; 2, determining a starting point for generating a strain hardening action and determining a terminal point for generating the strain hardening action; 3, determining two key points (Epsilon 1, Sigma 1), (Epsilon 2, Sigma 2) on the tensile curve; and 4, dividing a strain hardening interval into three sections by using the key points, respectively determining and comparing strain hardening indexes of the three sections, dividing one section with the maximum strain hardening index into three sections, respectively determining the strain hardening indexes of the three sections, and comparing the maximum strain hardening index of the three current sections with the maximum strain hardening index of the last circulation, if the error is in a specified range, determining the maximum strain hardening index of the three current sections as the strain hardening index of the material, and if the error is beyond the specified range, circulating till the error meets the provision. The method disclosed by the invention has the characteristics of high precision, controllable precision according to the demands and freedom of influences of personal factors.

A method for determining a strain hardening property of a pipe enabling reduction of costs while ensuring pipeline integrity is provided. Moreover, a method for manufacturing a pipe based on the method for determining the strain hardening property of the pipe, a pipe manufactured by means of the method for manufacturing the pipe, and a pipeline are proposed. The method for determining the strain hardening property of the pipe according to the present invention includes a step of defining pipe dimensions where a diameter D, a thickness t, and a required critical local buckling strain εreq of the pipe are set as conditions to be satisfied; a step of acquiring a strain hardening property for acquiring the strain hardening property in the vicinity of a buckling point of the pipe satisfying the conditions set in the step of defining the pipe dimensions; and a step of setting the strain hardening property as a condition to be satisfied by the stress-strain curve of the pipe.

The invention belongs to the field of building material, and especially relates to applications of an ECC material in recycled aggregate reinforcement, a recycled reinforced aggregate, and a preparation method and applications. The ECC material is excellent in strain hardening characteristic after being hardened, and multiple crack cracking is caused under stretching effect, so that the ECC material is capable of improving the quality of recycled aggregate obviously. The recycled reinforced aggregate is disclosed, and comprises a recycled aggregate, and an ECC layer used for coating the surface of the recycled aggregate; the ECC layer is adopted to fill recycled aggregate pores and coat the surface, so that a compact interface transition zone is formed, and the mechanical properties of therecycled aggregate are improved. The preparation method is capable of improving concrete ductility, and increasing energy consumption level of concrete structures under static force and dynamic loading. It is shown by tests that the 28d crush index of the recycled reinforced aggregate is 12.21%, and 28d compressive strength reaches 49MPa.

A polypropylene composition suitable for foaming having improved processability but maintained strain hardening and the process to produce the polypropylene composition comprising combining a linear polypropylene having a melt strength within a range from 10 to 40 cN (190DC) with an organic peroxide to obtain a branched polypropylene having a melt strength within a range from 20 to 80 cN (190DC), wherein the melt strength of the branched polypropylene is greater than the melt strength of the linear polypropylene; and combining the branched polypropylene having a melt flow rate within a range of 0.1 to 20 g / 10 min and an Mw / Mn of at least 5 with within a range from 5 to 40 wt% of a low molecular weight polyolefin having a melt flow rate of at least 50g / 10 min and an Mw / Mn of less than 5 to obtain the polypropylene composition.

The invention provides strip steel with excellent low-temperature secondary machining performance and the tensile strength being 370 MPa level. Components of the strip steel with the excellent low-temperature secondary machining performance and the tensile strength being 370 MPa level comprise, by weight, 0.0008-0.0028% of carbon, 0.07-0.10% of silicon, 0.30-0.50% of manganese, 0.04-0.055% of phosphorous, smaller than or equal to 0.008% of sulphur, 0.02-0.045% of aluminum, 0.02-0.06% of titanium, 0.006-0.022% of niobium, 0.0005-0.0013% of boron and smaller than or equal to 0.002% of nitrogen.Production of the strip steel comprises the steps of smelting and casting into billets, heating the cast billets, rough rolling, finish rolling, coiling, cold rolling after acid pickling, continuous annealing treatment, slow cooling, rapid cooling, aging treatment and levelling. According to the strip steel with the excellent low-temperature secondary machining performance and the tensile strengthbeing 370 MPa level, under the premise that the mechanical property is guaranteed, the plastic strain ratio ranges between 1.8 and 2.0 r90, and the strain hardening exponent ranges between 0.2 and 0.21 n90; the secondary machining brittle transition temperature is stabilized between minus 60 DEG C and minus 70 DEG C; the quantity of the titanium element and the niobium element is reduced so thatthe cost is lowered by 5% or more; no carbonized edges or bonding defects exist on the steel plate surface; and the strip steel is used for automobile outer covering parts used in more severe cold areas.

The invention discloses a method for determining uniaxial stress-strain relationship of a material based on a high-temperature hydraulic bulging sample test, and the method comprises the following steps: preparing a test sample, carrying out a hydraulic bulging test on the test sample to obtain a pressure center deflection test curve of the test sample, and obtaining an external force work centerdeflection curve of the sample based on the pressure center deflection test curve, obtaining the yield strength and the strain hardening index of the material by utilizing the external force work center deflection curve, and further determining the uniaxial stress-strain relationship of the material. According to the method for determining the uniaxial stress-strain relationship of the material, the uniaxial stress-strain relationship of the material is obtained through a hydraulic bulging micro-sample test technology, and material parameters of the uniaxial stress-strain relationship curve ofthe material can be obtained only by simply analyzing and calculating a pressure center deflection test curve obtained through the test; the obtained result is high in precision, a large number of tests are not needed, the test method and the test principle are relatively simple, and engineering application is very convenient.