Question

Which of the following controls "Koshi" in fabric low stress mechanical properties?

• A. Shear deformation
• B. Bending deformation
• C. Tensile deformation
• D. Surface deformation

Hint:

• Koshi (ハリ・コシ) Japanese fabric hand term meaning stiffness, crispness, springiness, anti-drape.
• It is one of the primary hand values assessed by systems like KES-F.
• Koshi is most strongly correlated with the bending properties} of a fabric, particularly bending rigidity (B) and bending hysteresis (2HB).
• Other KES-F primary hand values include Numeri (smoothness, related to surface properties) and Fukurami (fullness/soft bulkiness, related to compression and thickness).

Answer 1

The Correct Option is B

"Koshi" (ハリ・コシ) is a Japanese term used in evaluating fabric hand (Nameri). It is one of the primary hand values often derived from KES-F (Kawabata Evaluation System for Fabrics) measurements. Koshi is generally translated as stiffness, crispness, or anti-drape stiffness. It refers to the feeling of springiness, resilience, and resistance to bending. A fabric with high Koshi feels stiff and springy, recovers well from deformation, and doesn't drape softly. The KES-F system measures various low-stress mechanical properties:

• Tensile properties (related to extensibility, formability)
• Bending properties (related to stiffness, drape)
• Shear properties (related to drape, conformability)
• Compression properties (related to thickness, softness, bulkiness)
• Surface properties (related to smoothness, friction)

Koshi, as a perception of stiffness and springiness, is most directly related to the fabric's resistance to bending and its ability to recover from bending. The KES-F parameters primarily associated with bending are:

• B (Bending Rigidity): The resistance of the fabric to bending. Higher B means a stiffer fabric.
• 2HB (Bending Hysteresis): The energy loss during a bending cycle, related to the fabric's ability to recover from bending.

These bending parameters are key inputs into the calculation or assessment of Koshi. Let's evaluate the options:

• (a) Shear deformation: Shear properties (like G, 2HG) primarily relate to fabric drape, suppleness, and how well it conforms to a shape. While it contributes to overall hand, Koshi is more specifically tied to bending.
• (b) Bending deformation: This is directly related to stiffness and resilience from bending, which are the core aspects of Koshi.
• (c) Tensile deformation: Tensile properties (like LT, WT, RT) relate to how a fabric stretches and recovers from stretching. This contributes to feelings like "firmness" or "fullness" but is distinct from the crisp, springy stiffness of Koshi.
• (d) Surface deformation: Surface properties (like MIU, SMD) relate to smoothness, roughness, and friction. These contribute to surface feel (e.g., "Numeri" - smoothness, "Fukurami" - fullness involving surface) but not primarily to Koshi.

Therefore, Koshi is primarily controlled by bending deformation properties. \[ \boxed{\text{Bending deformation}} \]