Poly-xylyleneadipamide, made of 85 mole % m-xylylenediamine, 15 mole % p-xylylene-diamine and adipic acid, was extruded into undrawn filaments. The relationship between molecular orientation and crystallization of undrawn filaments and their mechanical properties were discussed, and the following results were obtained:
1) When undrawn filaments having the birefringence less than 3×10^-3 are dipped in water or treated in hot air, molecular chains crystallize in random orientation. On the other hand, when undrawn filaments having the birefringence more than 6×10^-3 are treated in the same way, molecular chains crystallize in oriented state.
2) When undrawn filaments are tested by the impact test method, filaments having low birefringence break at the yield point. On the other hand, filaments having high birefringence undergo plastic deformation, without breaking at the yield point.
3) The tenacity at the breaking point of undrawn filaments takes the maximum value when their birefringence is between 3 and 5×10^-3.

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The shear deformation property of two-bar tricot fabrics is analyzed, and the theory for calculating this property is dereloped by using a structural model. A unit structure of the model is constructed of three arcs of front-bar yarn and three arcs of back-bar yarn, and these arcs are stretched under shear deformation. This theory covers the general shear deformation of fabrics, for example, simple shear deformation, shear deformation under biaxial tensile deformation.
In this theory, the forces for stretching the fabric; are calculated from the forces required for straightening the arcs, while the frictional effect between yarns is taken into consideration, but the elongation and the compressive properties of yarn are out of consideration. The structure constants required for calcualation can be obtained easily from wale density, course density, fabric weight and yarn count.

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The load input tensile tester, the performance of which is not influenced by the mechanical properties of the material to be tested, was constructed. Its ability is investigated experimentally, to show the following results.
1) To avoid the velocity error the servo mechanism should satisfy the inequality:
1/K_s+K_pƒ<<K_mK_ƒ
2) To avoid the influence of the material properties to be tested, the hydraulic servo system should satisfy the inequality:
(A²/K₂)K_pƒ>>1
3) To make _??_ performance of the tester independent of the material properties to be tested, a compensation circuit of the servo system should satisfy the conditions:
K₀T₂T_pƒ>>K_pƒT₁
G_c(s)=(T₂s+1)/(T₁s+1), T₂>T₁

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