TYPES OF DEFECTS IN TIMBER

Types of Defects in timber are grouped into the following divisions.

1.Defects due to conversion

During the process of converting timber to commercial form, the following defects may occur.

• 芯片标记：在木材成品表面上芯片放置的标记或标记
• Diagonal grain:Due to improper sawing of timber
• Torn grain:Due to falling of tool small impression is formed
• Wane:Presence of original rounded surface on the manufactured piece of timber

2.Defects due to fungi

The attack of timber by fungi when moisture content of timber is above 20% and presence of air and warmth for the growth of fungi the following defects are caused

• Blue stain:Sap of wood is stained to bluish colour
• Brown rot:Decay or disease of timber by removal of cellulose compounds from wood and wood assumes the brown colour
• Dry rot:将木材转化为干粉形式
• Heart rot:This is formed when branch has come out of a tree and the tree becomes weak and gives out hallow sound when struck with a hammer
• Sap stain:The sap wood looses its colour because of feed on cell contents of sap wood.
• Wet rot:Caused chemical decomposition of wood of the timber and timber converts to greyish brown powder known as wet rot.
• White rot:攻击木材和木材的木质素假设白色质量的外观。

3.Defects due to insects

• 甲状腺虫: Small insects form holes of size about 2mm diameter and attack sap wood of all species of hard woods. Tunnels are formed in all directions in sapwood by the larvae of these beetles and converted into fine flour like powder. They do not disturb outer cover and looks sound.
• Marine borers：这些在木材中制作孔或钻孔隧道以避难所。由海洋螟虫袭击的木材失去了颜色和强度
• Termites: White ants are very fast in eating away the wood from the core of the cross section. They make tunnels inside in different directions and usually donot disturb the outer shell or cover

4.Defects due to natural forces

负责造成木材缺陷的主要自然力量是组织的异常生长和提高

• 伯：由于年龄较小的震惊，木材体内的不规则预测
• Callus: Soft tissue or skin which covers the wound of tree.
• Chemical stain: Discoloured due to the chemical action caused
• Coarse grain：每年戒指加宽，树迅速增长，木材具有更低的力量
• Dead wood: Timber obtained from dead standing tree
• Druxiness: White decayed spots by fungi
• Foxiness: Due to poor ventilation during storage or by commencement of decay due to over maturity indicated by red or yellow tinge in wood
• Knots: Bases of branches or limbs which are broken or cut off from the tree as shown in the fig-1.

• Rind galls：Rind意味着树皮和胆表明树上发现的异常生长和特殊的弯曲肿胀。
• 摇: These are cracks which partly or completely separate the fibres of wood as shown in fig-2.

• Twisted fibres/ W安德利果汁的心: caused by twisting of young trees by fast blowing wind as shown in fig-3.

• Upsets or ruptures：表示通过压碎或压缩损伤的木纤维，如图4所示。

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