GB/T 155-2017 in English
VALIDDefects in logs
- Issued on:2017-12-29
- Implemented on:2018-07-01
- File Format:PDF
- Delivery:Via email within 5 business days
Price(USD)：
$370.00
$359.00
$359.00
《GB/T 155-2017原木缺陷》由TC41（全国木材标准化技术委员会）归口，TC41SC2（全国木材标准化技术委员会原木和锯材分会）执行，主管部门为国家林业和草原局。
Introduction
Interpretation of the National Standard of the People's Republic of China for Log Defects GBT 155—2017
| Classification Dimensions | Specific Categories | Detailed Description | Impact Analysis |
|---|---|---|---|
| Knots | Live knots, dead knots, sound knots, decayed knots, missing knots, surface knots, hidden knots, whorled knots, scattered knots, clustered knots | Knots are the wood structures of tree branches, classified according to the degree of connection, material, growth location and distribution. Live knots are hard, while dead knots are separated from the surrounding wood. Healthy knots have no decay, decayed knots have decayed but not deep into the trunk, and missing knots go deep into the trunk and cause internal decay. Surface knots are exposed, while cryptogenic knots are hidden under the bark. | Knots affect the strength and processing properties of wood, especially dead knots and missing knots may cause serious defects and reduce the utilization value of wood. |
| Cracks (shake) | End cracks, radial cracks, single radial cracks, multiple radial cracks (star cracks), ring cracks, ring cracks, arc cracks, longitudinal cracks, frost cracks, shock cracks, dry cracks, through cracks, and explosion cracks | Cracks are divided into end cracks and longitudinal cracks according to their locations. End cracks include radial cracks and ring cracks, and radial cracks are divided into single radial cracks and multiple radial cracks. Ring cracks crack along the direction of the growth ring. Longitudinal cracks are caused by frost cracks, shock cracks or dry cracks, through cracks penetrate the pith, and explosion cracks form multiple cracks. | Cracks seriously weaken the strength of wood, especially through cracks and bursts, which significantly increase the waste rate of processing. |
| Defects of trunk shape | Bending, root hypertrophy (large pocket, concave pocket), ellipsoid, tapering | Bending can be divided into unidirectional and multi-directional, which affect the yield and strength of wood processing. Root hypertrophy mostly increases the cross-section of the log, and the ellipsoid leads to a significant difference in length and width. Tapering is manifested as a gradual decrease in the diameter of the trunk. | These defects directly affect the appearance and mechanical properties of wood, especially in structural materials, the degree of bending must be strictly controlled. |
| Defects of wood structure | Twisted grain, random grain, stress wood (compression wood, tension wood), double-heart or multi-heart wood, eccentric wood, eccentric withering, bark, tree bag, tree knot, pseudo-heartwood, internal sapwood | Twisted grain and random grain destroy the arrangement of wood fibers and affect processing performance. Stress wood changes in strength due to uneven force. Compression wood and tension wood correspond to abnormal growth of conifers and broad-leaved trees respectively. Double-heart or multi-heart wood is characterized by a large number of piths that grow independently, while eccentric wood has piths that deviate from the center. | These defects affect the uniformity and processing performance of wood. Some structures such as knots can be used as high-end decorative materials. |
| Defects caused by fungi | Fungal discoloration and decay | Fungal discoloration includes abnormal color changes of heartwood and sapwood, such as green discoloration and asphyxial browning. Decay is divided into white rot, brown rot and soft rot according to type, which affects the physical and mechanical properties of wood. Decay causes structural damage to wood and greatly reduces its strength. | Fungal defects significantly reduce the use value of wood, and storage and transportation conditions must be strictly controlled to reduce their occurrence. |
Implementation suggestions
1. Preventive measures:
- Strengthen forest health monitoring and deal with sick and weak trees in a timely manner.
- Reasonable felling to reduce mechanical damage and human damage.
- Optimize storage and transportation conditions to avoid wood being exposed to moisture, high temperature or insects.
2. Detection methods:
- Use professional instruments to detect wood defects, such as ultrasonic testing equipment to detect internal cracks and decay.
- Combining visual inspection and laboratory analysis to determine the extent of fungal infection.
- Use X-ray imaging technology to assess the internal structural integrity of the wood.
3. Processing:
- Minor defects such as small knots and surface cracks can be repaired by sanding or milling.
- For severely decayed parts, it is recommended to cut off and reuse the remaining intact wood.
- Use preservatives to treat fungal infected wood to extend its service life.
Sample only — not a preview of GB/T 155-2017
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